Superior Magnetoresistance Performance of Hybrid Graphene Foam

Subscriber access provided by UNIV OF LOUISIANA

Applications of Polymer, Composite, and Coating Materials

Superior Magnetoresistance Performance of Hybrid Graphene Foam/Metal Sulfide Nanocrystal Devices M. Husnain Zeb, Babar Shabbir, Rizwan Ur Rehman Sagar, Nasir Mahmood, Keqiang Chen, Irfan Qasim, Muhammad Imran Malik, Wenzhi Yu, M. Mosarof Hossain, Zhigao Dai, Qingdong Ou, Masroor A. Bhat, Bannur Nanjunda Shivananju, Yun Li, Xiang Tang, Kun Qi, Adnan Younis, Qasim Khan, Yupeng Zhang, and Qiaoliang Bao ACS Appl. Mater. Interfaces, Just Accepted Manuscript • Publication Date (Web): 26 Apr 2019 Downloaded from http://pubs.acs.org on April 26, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

SUPERIOR MAGNETORESISTANCE PERFORMANCE OF HYBRID GRAPHENE FOAM/METAL SULFIDE NANOCRYSTAL DEVICES M. Husnain ZebΔ,Ω, Babar ShabbirΔ,§, Ω,*, Rizwan Ur Rehman Sagarж, Ω, Nasir MahmoodΘ, Keqiang ChenΔ, Irfan Qasim∞, Muhammad Imran Malik◊, Wenzhi Yu§, M. Mosarof Hossain§, Zhigao Dai§, Qingdong Ou§, Masroor A. BhatϞ, Bannur Nanjunda ShivananjuΔ,§, Yun Li§, Xiang TangΔ, kun QiΔ,§, Adnan Younis‡, Qasim KhanΔ, Yupeng ZhangΔ* and Qiaoliang Bao§*

ΔKey

Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Electronic Science and Technology and College of Optoelectronics Engineering, Shenzhen University, Shenzhen University, Shenzhen 518060, People’s Republic of China §Department of Materials Science and Engineering, and ARC Centre of Excellence in Future LowEnergy Electronics Technologies (FLEET) Monash University, Clayton, Victoria 3800, Australia жGraduate School at Shenzhen, Tsinghua University, Shenzhen 518055, P. R. China ΘSchool of Engineering, RMIT University, 124 La Trobe Street, 3001 Melbourne, Victoria, Australia ∞Department of Physics, Riphah International University, Islamabad 44000, Pakistan ◊School of Electrical Engineering and Computer Science (SEECS) National University of Sciences and Technology (NUST) H-12, Islamabad 44000, Pakistan ϞShenzhen Key Laboratory of Polymer Science and Technology, College of Materials Science and Engineering, Shenzhen University, Shenzhen 518060, P. R. China ‡School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052, Australia KEYWORDS Graphene foam, Cu2ZnSnS4 nanocrystals, Magnetotransport, Magnetoresistance and Nanoboundaries.

Graphene

Foam

composites,

Magnetic

sensors,

ABSTRACT: Interfaces between metals and semiconducting materials can inevitably influence the magnetotransport properties, which are crucial for technological applications ranging from magnetic sensing to storage devices. By taking advantage of this, metallic graphene foam is integrated with semiconducting copper based metal sulfide nanocrystals i.e. Cu2ZnSnS4 (Copper-Zinc-Tin-Sulfur) without direct chemical bonding and structural damage, which creates numerous nano-boundaries that, can be basically used to tune the magnetotransport properties. Herein, the magnetoresistance of graphene foam is enhanced from nearly 90% to 130% at room temperature and under the application of 5T magnetic field strength due to the addition of Cu2ZnSnS4 nanocrystals in high densities. We believe that the enhancement of magnetoresistance in hybrid graphene foam/ Cu2ZnSnS4 nanocrystals is due to the evolvement of the mobility fluctuation mechanism, triggered by the formation of nano-boundaries. Incorporating Cu2ZnSnS4 nanocrystals to graphene foam not only provides an effective way to further enhance the magnitude of magnetoresistance but also open a suitable window to achieve efficient and highly functional magnetic sensors with a large, linear and controllable response.

Introduction: The idea of magnetotransport phenomena has been substantially utilized in several technologies such as magnetic sensing

and storage devices, where the magnetoresistance (MR) behavior could evaluate the device performance and/or efficiency 1-3. Due to the high

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

demands of MR devices with high performance, cost-effective fabrication and low energy consumption, several new materials have been explored. Atomically thin Graphene, probably a most exciting electronic material that revealed many stimulating properties including giant electron mobility4, extremely high thermal conductivity5, and especially large MR values6. At room temperature and high fields (~10T), a linear positive magneto-resistance (LPMR) ~ 70% is reported for multilayer epitaxial graphene and well above 60% for few layers graphene stacks with current perpendicular to plane geometry7. Furthermore, large LPMR in order of hundred has also been found in single layer graphene flakes8. Notably, morphology and structure of graphene could manipulate its electro/magneto transport properties9. While graphene shows high MR values, the quality of the produced graphene will still be the major challenge to its commercial applications. The production of high-quality graphene is expensive and involves a complicated process to control the impurities, doping levels, domain size, number of layers and their relative crystallographic orientation. Also, attempts to synthesize graphene macrostructures could yield materials/devices with low 10 conductivities . Two dimensional (2D) materials generally require sophisticated and hierarchical threedimensional (3D) architectures, to be used in macroscopic devices. Eventually, 3D architectures of 2D materials have demonstrated high mechanical stability, specific surface areas, and fast mass & electron transport characteristics11-12. The ideal example is 3D Graphene Foam 1 (GF), porous and metallic foam with highsurface-area form of graphene. GF incorporates the distinctive mechanical and electrical properties of 2D graphene and as a result, GF is highly conductive and have an excellent mechanical strength when integrated with polymers13. Additionally, GF can also be produced on a gram scale and therefore, GF could be an exciting material for future MR devices. Meanwhile, GF shows large MR values of nearly 90% at 5T and room temperature14 but

Page 2 of 17

progress in this area is required to further increase the MR beyond its highest achieved value to enhance the device performances. Generally, several techniques have been used to tailor the material’s physical properties such as pressure 15-19, doping/addition or integration among different materials20-22 and so on. Unlike pressure approach, the integration among different materials or creating interfaces appears to be an effective approach to improve the device performance without damaging a material. In this work, we demonstrated a significant enhancement in magnetotransport properties of a GF by utilizing CZTS nanocrystals. Specifically, the cost-effective, environmentally friendly and small band gaps Cu2ZnSnS4 nanocrystals (CZTS) illustrates the best set of parameters23, with clear potential to tailor the magnetotransport properties. Owing to a reported positive MR by CZTS crystals24, this material is well-suited to enhance the PMR of GF. Without modifying the GF morphology, CZTS nanocrystals with various densities (corresponds to nanocrystals absorption time 1, 3 and 5mins) are integrated with GF. The high density of CZTS nanocrystals can significantly enhance the MR of GF from nearly 90 to 130% at room temperature and magnetic field strength of 5T. Enhancement in MR is strongly interconnected to the mobility fluctuation mechanism. It is worth mentioning here that linear, large and unsaturated MR response of GF/CZTS not only provides an effective way to further enhance magnitude of MR but also open a suitable window to achieve efficient and highly functional magnetic sensors with a large, linear and controllable response. Results

2 ACS Paragon Plus Environment

Page 3 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 1: (a) The XRD spectrum of CZTS shows three broad peaks positioning at 2Ө of 28.26⁰, 47.28⁰, 55.24⁰ corresponds to the (112), (220), (312) planes revealing that the assynthesized CZTS has small crystallite size (b) Raman spectrum for few-layer GF and CZTS with prominent peaks. The peaks present in the lower wavenumber of 50-400 cm⁻1 are confirming the presence of Nanocrystals on graphene sheets with CZTS composition.

The morphological studies of GF and GF/CZTS are carried out by using SEM (Fig. S1: Supporting Information). The GF fabricated via CVD has a 3D structure having large pores of ∼30–100 μm constructing a network analogue to that of the nickel foam, while the surface of graphene sheets is smooth. After the injection of CZTS nanocrystals into GF, the smooth surface of graphene sheets turned to rough confirming the fine distribution of CZTS nanocrystals in the network of GF as shown in Fig. S1(f). To estimate CZTS contents in a composite, we performed energy dispersive spectroscopy (EDS) analysis as shown in supporting information figures S2, S3 and S4. Fig. S4 clearly indicates the large contents of CZTS nanocrystals in GF/CZTS-5min composites as compared to other specimens as shown in Fig. S2 and Fig. S3. The crystalline structure of GF/CZTS is analyzed by XRD and Raman spectroscopy, shown in Fig. 1(a) and 1(b). The XRD spectrum of CZTS shows three broad peaks positioning at 2Ө of 28.26⁰, 47.28⁰, 55.24⁰ corresponds to the (112), (220), (312) planes revealing that the assynthesized CZTS has small crystallite size. The CZTS has tetragonal type kesterite structure of Cu2ZnSnS4 according to standard card No. 260575, where each sulphur anion is surrounded by the four cations and vice versa. Fig.1(b) displays a Raman spectrum for few-layer GF and GF/CZTS composite with prominent peaks for CZTS present in the lower wavenumber of 50400 cm⁻1 can confirm the presence of nanocrystals on graphene sheets with CZTS composition23. Also, G peak intensity is found more than 2D peak, indicating few layer graphene in our case25-26. To further explore the structure and distribution of CZTS nanocrystals on the graphene foam, transmission electron microscopic (TEM) studies were conducted and

results are shown in Figure 2. Figure 2a clearly shows the smooth and well-defined sheets of graphene, while their high-resolution TEM (HRTEM, Figure 2b) analysis reveals the lattice spacing of ~ 0.308 nm corresponds to the interlayer distance of graphene. The selected area electron diffraction (SAED) shows a diffraction pattern of graphene geometry, where, fused circular ring structure of SAED pattern confirming the networking of graphene sheets in GF (the inset of Figure 2b). The TEM image of GF/CZTS presents the homogenous distribution of CZTS nanocrystals on graphene sheets, where nanocrystals have the average particle size of 5 nm (Figure 2c). Further details for TEM of CZTS nanocrystals can be seen in Ref23.

Figure 2: (a) TEM image of GF and (b) HRTEM image of GF (the inset shows the SAED pattern of GF). (c) High magnification TEM image of GF/CZTS (the inset shows SAED pattern of GF/CZTS) and (d) HRTEM image of GF/CZTS which clearly shows the existence of highly crystalline CZTS nanocrystals.

The HRTEM analysis reveals the lattice spacing of 0.308 nm corresponds to (112) plane wellmatched with kesterite phase of CZTS according to standard pdf card No. 26-0575 as shown in Figure 2d. The SAED pattern shown in the inset of Figure 2c exhibits the diffraction rings with dspacing of 0.31 nm, 0.27 nm and 0.16 nm corresponds to (112), (220) and (312) planes of CZTS, respectively, well-matched with the XRD 3



observation. However, the presence of multiple rings may attribute to the random orientation of CZTS crystallites and coexistence of graphene, delineating strong adhesion among the components of hybrid. Therefore, the strong coherence observed from structural and morphological results confirming the high homogeneity of the GF/CZTS specimen, which produced numerous nanoboundaries and therefore, can tune the magnetotransport properties of our hybrid device.

Figure 3: (a-d) MR curves for GF, GF/CZTS specimens at different temperatures and fields. All curves show positive and linear MR responses and enhancement is observed for all GF/CZTS nanocrystals devices (e) MR enhancement from nearly 90% to 150% in highly concentrated GF/CZTS at 5K and 5T. (f) MR curves versus temperature for different specimens at 5T illustrates significant enhancement at different temperatures.

The MR curves for GF, GF/CZTS-1min or Low Concentration (LC), GF/CZTS-3mins or Medium Concentration (MC) and GF/CZTS5mins or High Concentration (HC) at different temperatures and fields are shown in Fig.3(a-d).

Page 4 of 17

While the MR of GF strongly depends on the porosity of a Nickel foam, therefore our MR values are slightly less than an earlier report14 as we used Ni foam with porosity 100 PPI (i.e. pores/inch). The obtained MR at relatively small fields tends to be quadratic, like the classical MR in semiconducting or conducting materials. Albeit rough, MR becomes linear with field beyond 2T, which can satisfy Abrikosov’s conditions for quantum linear 27 magnetoresistance . In comparison to GF, large MR values can be seen in LC, MC and HC specimens. For example, high values of nearly 150% are found for HC specimen at 5K (Figure 3e). Almost a similar trend in the enhancement of MR is observed at same field (5T) but other temperatures i.e. 50K, 100K, 200K & 300K and data is plotted in Figure S5 (Supporting Information). Here, it is important to mention that our obtained results are superior to mostly other graphene-based devices as indicated in Table S1 (Supporting Information). Also, enhancement of MR in GF/CZTS devices at different temperatures and 5T can be seen in figure 3f. Although experimental data for MC and HC predicts a nearly saturation regime at high CZTS nanocrystals densities, but the key point is that obtained MR in hybrid devices are well above 100%, even persists up to room temperatures with linear responses. This could open a possibility to manufacture GF based magnetic sensors which can operate at room temperature where no cooling is required for their applications and especially with unsaturated and linear responses.

Discussion GF is a sophisticated and hierarchical 3D architecture of graphene; therefore, we can explain its magnetotransport phenomena based on graphene. The MR linked to the weak localization in multiple layer graphene is expressed as28


Page 5 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


∆𝜌(𝐵) ≡ 𝜌(𝐵) ―𝜌(0) = ―

[𝐹( ) ― 𝐹 ( 𝐵 𝐵𝜑

Here

) ― 2𝐹 (

𝐵 𝐵𝜑 + 2𝐵𝑖

𝐵 𝐵𝜑 + 𝐵 *

(12 + 1𝑧),

𝐹(𝑧) = ln (𝑧) + 𝜓

(𝑒𝜌)2 𝜋ℎ

to local current density in both magnitude and direction due to microstructures generated by nonhomogeneous carrier and mobility distribution.

)] (1)

𝐵𝜑, 𝑖,

ℎ𝑐

*

= 4𝐷𝑒

𝜏𝜑,―1𝑖, * . 𝜓 ― digamma function, D is a diffusion constant, ℎ ― plank’s constant, 𝜌(𝐵) and 𝜌(0) ― resistivities in the presence and absence of magnetic fields respectively. Wu et al. 29 included the influence of isospin conserving scattering mechanism therefore; the correction to the sheet MR in eqn. 1 can be shown as

[( ) (

) (

)]

(𝑒𝜌)2 2𝜏𝜑 2 2 ∆𝜌(𝐵) ≡ ― 𝐹 ―𝐹 ― 2𝐹 (2) 𝜋ℎ 𝜏𝐵 𝜏𝐵(𝜏𝜑―1 + 2𝜏𝑖―1) 𝜏𝐵(𝜏𝜑―1 + 𝜏𝑖―1 + 𝜏𝑤―1) Here 𝜏𝜑 ― the phase coherence time; 𝜏𝑖 ― the intervalley scattering time; here long range scattering potential is linked to the charge scatterers and dislocations/defects; 𝜏𝑤 ― the warping-induced relaxation time, correlated to an intra-valley scattering because of the trigonal warping effect; 𝜏𝐵 = ℏ 2𝑒𝐷𝐵 . The weak or anti weak localization (WL, AWL) is strongly connected to the negative and positive linear MR in graphene28-30. Generally, the weak localization MR is connected to two types of scattering rates i.e. Elastic (chiralitybreaking, 𝜏𝑖, 𝜏𝑤) and In-elastic (phase-breaking “ 𝜏𝜑"). The 𝜏𝐵 increase as the Fermi energy expands and that can be related to a specific degree of backscattering in the valley. The first term in eqn (2) is related to WL, whereas; the second and third terms with negative sign are linked to AWL. The obtained PMR curves therefore, correspond to WAL in our case. This can be linked to the suppression of the (a) WL because of the decreased intervalley scattering and (b) backscattering due to presence of the Berry phase28. Due to the inherent chiral nature of electrons, backscattering of carriers in exactly the same direction by the charges trapped on graphene layers is unattainable 31. Additionally, linear MR can be found in classical disorder systems is another evidence32. The linear MR originates because the spatial fluctuations linked

Figure 4: (a) provides a graphical scheme for the MR measurements. (b) Schematic for graphene foam (c) Integration of Cu2ZnSnS4 nanocrystals and Graphene foam (d,e) shows the evolution of mobility fluctuation mechanism due to the formation of nanoboundaries, by the integration of Cu2ZnSnS4 Nanocrystals and Graphene foam. Large MR in GF/CZTS is observed due to strong mobility fluctuations. Both materials are measured by using a special homemade PPMS puck (Figure S6) in current voltage (IV) geometry.

On the other hand, significant MR enhancement especially linear and large, in different hybrid systems is caused by strong mobility fluctuations33. Figure 4 shows a schematic illustration of GF/CZTS and evolvement of mobility fluctuation mechanism in hybrid devices. GF is composed of monolayer; bilayers to multilayers and the addition of CZTS nanocrystals originate numerous nanoboundaries. Mobility of carriers can easily be perturbed by these nanoboundaries. The magnitude and the 5



linearity of the MR can be determined by the nature of the mobility distribution. At relative high magnetic fields, we can write32 𝑀𝑅 ∝

{〈𝜇〉, ∆𝜇,

∆𝜇 〈𝜇〉 < 1 ∆𝜇 〈𝜇〉 > 1 (5)

Here ∆𝜇 ~ width of the mobility disorder and 〈𝜇〉 is termed for average mobility. At field 〈𝜇〉 ―1 for ∆𝜇 〈𝜇〉 < 1 and (∆𝜇) ―1 for ∆𝜇 〈𝜇〉 > 1, the crossover behavior from linear to quadratic is noticed. Noticeably, integration of CZTS nanocrystals with GF indicates cross over from linear to quadratic trend at extremely low fields, which is similar to a disordered semiconductor where a obtained crossover field of a system at the characteristic field 〈𝜇〉 ―1~1𝑇 is smaller by several orders of magnitude, provided ∆𝜇 is large34.

Figure 5: (a) MR(%) vs B2 is plotted at different temperatures in order to calculate the mobility for GF/CZTS-5min. Similar method is used to obtain the mobilities for other specimens. A low field indicates parabolic drifts (due to the electron

Page 6 of 17

trajectory being distorted under Lorentz forces) while linear trends are realized at high fields as marked in different colour sections (b) shows mobility values at different temperatures and different specimens. An increase in mobility values are calculated in hybrid GF/CZTS devices with HC specimen being the highest.

Classically, magnetoresistance dependence on mobility is defined as14 MR ∝ (μB)2 (3) here, μ is used for the mobility, B is for the applied magnetic field, termed as quadratic MR co-efficient. The μ can be determined by using a well known straight line equation i.e. A = mx + c . Figure 5a represents a classical plot for MR vs. B2 to determine the mobilities for different specimens. Albeit rough, the multiple trends in the curve are distinguished by coloured domains. A low field indicates parabolic drifts (due to the electron trajectory being distorted under Lorentz forces) while linear trends are realized at high fields. GF includes multiple conduction regimes because of the randomly oriented few-layer graphene with different sizes and orientations. Indeed, these conduction regimes could be governed by the addition of CZTS nanocrystals because magnetotransport properties are sensitive to interfaces, defects, boundaries, and perturbed electron clouds35. Figure 5b illustrates μ values for LC, MC and HC specimens at different temperatures. The obtained μ values are inversely proportional to the temperature values i.e. low mobility values at high temperatures, well aligned with parallel MR values. Additionally, high mobilities can produce large mobility fluctuations due to increase number of scatterings. At 5K, the μ is increased from 2.11(104cm2/V.s);GF to 4 2 4 2 2.22(10 cm /V.s);LC, 2.32(10 cm /V.s);MC and 2.43(104cm2/V.s) (HC). While GF;μ~1.74, LC;μ MC;μ~2.14 and MC;μ~2.27 ~1.95, (104cm2/V.s) is found at room temperature. Similar enhancement trend is also obtained for other temperatures and therefore reflects MR enhancement based on mobility fluctuation mechanism. Our μ values are in an excellent agreement with the other quantum mobility 6


Page 7 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


results36. The quantum mobility can be estimated by using the following relation μq = eνFτq/hkF (4) where, νF is a Fermi velocity, "kF" a Fermi wave vector and τq is a quantum lifetime, found by using a Dingle temperature “𝑇𝐷”. The semi2π2KBT ∆R logarithmic plot of R(0)sinh ∆EN

(

)

versus 𝐵 ―1 can be used to estimate the values of 𝑇𝐷. Here ∆EN is a Landau level difference. In comparison to GF, high μ values in GF/CZTS specimens results in more scatterings which inturn indicates strong mobility fluctuation mechanism and resistance versus temperature graph is another evidence of that (Plotted in Supporting information as a Figure S7a). It is also important to mention here that experimental "μ" can be determined by Hall measurements. The uniform geometry of a material is used to deduce the accurate μ values. In our case, we are not able to measure the hall mobility accurately because of irregular GF geometry i.e. porosity and uneven surface. Also, MR enhancement is not interrelated to some magnetic effects because obtained magnetic hysteresis curves are almost same for GF and GF/CZTS specimens (Figure S7b). Conclusion We demonstrated an effective approach i.e. integration of GF with CZTS nanocrystals, to significantly enhance the linear positive magnetoresistance of GF. The high density of CZTS nanocrystals tuned the magnetoresistance of GF from nearly 90 to 130% at room temperature and 5T. We believe that the mobility of carriers can be easily perturbed by creating numerous nano-boundaries via addition of nanocrystals. Integration of CZTS with GF not only provides an effective way to tune magnitude of LPMR and it also opens a suitable window to achieve efficient and highly functional magnetic sensors with a large, linear and controllable response. 7 ACS Paragon Plus Environment


Experimental Section Synthesis of GF Chemical Vapor Deposition (CVD- GSL-1700X, MTI) method was used for the synthetization of graphene foam, with Nickel foam as a base material10. Nickel foam with 100 PPI (pores per inch) was purchased commercially. PPI is measured as an average across the surface of the material in its uncompressed form. This is reticulated foam which means the pore density (uncompressed) would be the same in all dimensions. In CVD, there are four steps involved; placing nickel foam in furnace tube, creating vacuum in the furnace tube, the increment of temperature and utilization of gases. Using nonmagnetic rod, nickel foam (100 PPI) on alumina boat was positioned at the center of the furnace tube. Rotary pump was used to create the vacuum ~ 10-1 torr. Then the temperature inside the furnace tube was increased from room temperature to 1100°C with step of 10 °C/min. Finally, during the experiment, a combination of argon (75%) and hydrogen (25%) gases flow was maintained at a specific rate 100 sccm (standard centimeter cube per minute). At 1100°C, substrate annealing was completed for 10 mins and an ethylene (C2H4) gas was mixed with already provided gases at the rate ~ 200 sccm. Later, we transferred the GF by etching nickel foam, using FeCl3 and HCl in deionized water. After the removal of nickel, GF came up on the solution surface due to its low density and we waited nearly 48hrs for the totally elimination of nickel residuals. The final product was immersed in acetone for several days and later dried at 60°C and 24hrs, using an oven. Synthesis of Cu2ZnSnS4 (CZTS) nanocrystals CZTS nanocrystals can be obtained through a typical hot-injection method. Briefly, oleylamine (20 mL, OLA), CuI (1 mmol), Zn(ac)2 (0.5 mmol), and SnCl4·5H2O (0.5 mmol) were loaded into a 50 mL three-neck flask and heated to 150 ℃ under Ar atmosphere, a clear slightly yellow solution would be obtained. Subsequently, the system temperature was set to 190 ℃, and 3 mL N,N'-diphenylthiourea dissolved in diphenyl

Page 8 of 17

ether (1 M) was swiftly injected into the above mixture, the reaction solution was stirred at 190 0C for 5 min and cooled to room temperature. 1 mL of the crude solution was added into 3 mL methanol and centrifuged at 8000 rpm for 3 min. After centrifugation, the supernatant was discarded, and the precipitate was re-dispersed into hexane (4 mL). Then, another centrifugation process was carried out to get high-quality CZTS NCs solution. GF/CZTS Nanocrystals Integration of GF with CZTS nanocrystals were achieved with the help of chemical dip coating. A concentrated solution of nanocrystals was prepared for this purpose and GF specimens were dipped in CZTS concentrations and wait for 1, 3 and 5 min (GF/CZST-1min, GF/CZST-3min, GF/CZST-5min) to have different absorption densities. Afterward, the specimens were placed at a low heating temperature ~ 50 C (high temperatures can affect CZTS nanocrystals) for 2 hours to let specimens dry. Characterization tools SEM-Hitachi, SU-70 (Scanning electron microscopy) was used to determine the morphology of GF and GF/CZTS specimens. Renishaw-HR800 (Raman spectroscopy) was employed to differentiate GF and GF/CZTS specimens. RAMAN spectra were obtained by using 532nm laser excitation source. Further analysis was carried out with the help of HRTEM, JEOL-2010 (High-resolution transmission electron microscope) and XRDRigaku D/max 2500, λ = 1.5406 Å (X-ray diffraction) with Cu-Kα irradiation. Magnetotransport properties were obtained by using PPMS-9T (Quantum Design; Physical Property Measurement System), equipped with a specially made puck as shown in Figure S6 (Supporting information) and MR was calculated by using standard formula i.e.𝑀𝑅(%) =

(

𝑅𝑥𝑥(𝐵) 𝑅𝑥𝑥(0)

)

― 1 𝑋100. Where Rxx(B) is a resistance

under applied magnetic field (B) and Rxx(0) is a resistance under zero B. We used 8


Page 9 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


10(L)X4(W)X3(H)mm3 (Material’s dimensions) for transport measurements. AUTHOR INFORMATION Corresponding Author

*Babar Shabbir (Email: babar.shabbir@ szu.edu.cn), Yupeng Zhang (Email: [email protected]) and Qiaoliang Bao (Email: [email protected]) Author Contributions

Ω These authors contributed equally to this work. Ω M. H. Zeb, Ω B. Shabbir and Ω R.U.R. Sagar collected the GF specimen characterization & magnetotransport data and co-wrote the manuscript. K. Qi, X. Tang and N. Mahmood performed TEM and analyzed the data. K. Chen provided CZTS Nanocrystals. M. A. Bhat and Q. Khan helped to perform the SEM. B. Shabbir and Y. Zhang supervised the project. Q. Bao is a head of a group. All the other authors helped in data interpretation and discussions.

ACKNOWLEDGMENT We acknowledge the support from the National Natural Science Foundation of China (No. 61875139, 91433107 and 51702219), the National Key Research & Development Program (No. 2016YFA0201902), Shenzhen Nanshan District Pilotage Team Program (LHTD20170006) and Australian Research Council (ARC, FT150100450, IH150100006 and CE170100039). B.S. acknowledges the funding support from China Postdoctoral Science Foundation Grant (No. 217M622758). R. U. R. Sagar would like to thank the National Natural Science Foundation of China (No.11850410427) for financial support. N. Mahmood would like to acknowledge the Vice Chancellor Research Fellowship Scheme at RMIT University for research funding.

SUPPORTING INFORMATION: Additional structural analysis, Magnetoresistance (MR), Resistance-Temperatures & Magnetic Hysteresis plots and MR comparison with other related materials.

REFERENCES

1. Wang, X.; Du, Y.; Dou, S.; Zhang, C., Room Temperature Giant and Linear Magnetoresistance in Topological Insulator Bi2Te3 Nanosheets. Physical Review Letters 2012, 108 (26), 266806. 2. Shabbir, B.; Nadeem, M.; Dai, Z.; Fuhrer, M. S.; Xue, Q.-K.; Wang, X.; Bao, Q., Long Range Intrinsic

Ferromagnetism in Two Dimensional Materials and Dissipationless Future Technologies. Applied Physics Reviews 2018, 5 (4), 041105. 3. Sagar, R. U. R.; Saleemi, A. S.; Shehzad, K.; Navale, S. T.; Mane, R. S.; Stadler, F. J., Non-Magnetic Thin Films for Magnetic Field Position Sensor. Sensors and Actuators A: Physical 2017, 254 (Supplement C), 89-94. 4. Novoselov, K. S.; Geim, A. K.; Morozov, S. V.; Jiang, D.; Katsnelson, M. I.; Grigorieva, I. V.; Dubonos, S. V.; Firsov, A. A., Two-Dimensional Gas of Massless Dirac Fermions in Graphene. Nature 2005, 438, 197. 5. Balandin, A. A.; Ghosh, S.; Bao, W.; Calizo, I.; Teweldebrhan, D.; Miao, F.; Lau, C. N., Superior Thermal Conductivity of Single-Layer Graphene. Nano Letters 2008, 8 (3), 902-907. 6. Bai, J.; Cheng, R.; Xiu, F.; Liao, L.; Wang, M.; Shailos, A.; Wang, K. L.; Huang, Y.; Duan, X., Very Large Magnetoresistance in Graphene Nanoribbons. Nature Nanotechnology 2010, 5, 655. 7. Liao, Z.-M.; Wu, H.-C.; Kumar, S.; Duesberg, G. S.; Zhou, Y.-B.; Cross, G. L. W.; Shvets, I. V.; Yu, D.-P., Large Magnetoresistance in Few Layer Graphene Stacks with Current Perpendicular to Plane Geometry. Advanced Materials 2012, 24 (14), 1862-1866. 8. Gopinadhan, K.; Shin, Y. J.; Yudhistira, I.; Niu, J.; Yang, H., Giant Magnetoresistance in Single-Layer Graphene Flakes with a Gate-Voltage-Tunable Weak Antilocalization. Physical Review B 2013, 88 (19), 195429. 9. Yue, Z.; Levchenko, I.; Kumar, S.; Seo, D.; Wang, X.; Dou, S.; Ostrikov, K., Large Networks of Vertical Multi-Layer Graphenes with MorphologyTunable Magnetoresistance. Nanoscale 2013, 5 (19), 9283-9288. 10. Chen, Z.; Ren, W.; Gao, L.; Liu, B.; Pei, S.; Cheng, H.-M., Three-Dimensional Flexible and Conductive Interconnected Graphene Networks Grown by Chemical Vapour Deposition. Nature Materials 2011, 10, 424. 11. Shehzad, K.; Xu, Y.; Gao, C.; Duan, X., ThreeDimensional Macro-Structures of Two-Dimensional Nanomaterials. Chemical Society Reviews 2016, 45 (20), 5541-5588. 12. Sagar, R. U. R.; Galluzzi, M.; García-Peñas, A.; Bhat, M. A.; Zhang, M.; Stadler, F. J., Large Unsaturated Room Temperature Negative Magnetoresistance in Graphene Foam Composite for Wearable and Flexible Magnetoelectronics. Nano Research 2018, 12(1): 101–107. 13. Nieto, A.; Dua, R.; Zhang, C.; Boesl, B.; Ramaswamy, S.; Agarwal, A., Three Dimensional Graphene Foam/Polymer Hybrid as a High Strength Biocompatible Scaffold. Advanced Functional Materials 2015, 25 (25), 3916-3924. 14. Sagar, R. U. R.; Galluzzi, M.; Wan, C.; Shehzad,



K.; Navale, S. T.; Anwar, T.; Mane, R. S.; Piao, H.-G.; Ali, A.; Stadler, F. J., Large, Linear, and Tunable Positive Magnetoresistance of Mechanically Stable Graphene Foam–Toward High-Performance Magnetic Field Sensors. ACS Applied Materials & Interfaces 2017, 9 (2), 1891-1898. 15. Shabbir, B.; Huang, H.; Yao, C.; Ma, Y.; Dou, S.; Johansen, T. H.; Hosono, H.; Wang, X., Evidence for Superior Current Carrying Capability of Iron Pnictide Tapes under Hydrostatic Pressure. Physical Review Materials 2017, 1 (4), 044805. 16. Shabbir, B.; Wang, X.; Ma, Y.; Dou, S. X.; Yan, S. S.; Mei, L. M., Study of Flux Pinning Mechanism under Hydrostatic Pressure in Optimally Doped (Ba,K)Fe2As2 Single Crystals. Scientific Reports 2016, 6, 23044. 17. Shabbir, B.; Wang, X.; Ghorbani, S. R.; Wang, A. F.; Dou, S.; Chen, X. H., Giant Enhancement in Critical Current Density, up to a Hundredfold, in Superconducting Nafe0.97Co0.03 As Single Crystals Under Hydrostatic Pressure. Scientific Reports 2015, 5, 10606. 18. Shabbir, B.; Wang, X.; Ghorbani, S. R.; Shekhar, C.; Dou, S.; Srivastava, O. N., Hydrostatic Pressure: A Very Effective Approach to Significantly Enhance Critical Current Density in Granular Iron Pnictide Superconductors. Scientific Reports 2015, 5, 8213. 19. Shabbir, B.; Wang, X. L.; Ghorbani, S. R.; Dou, S. X.; Xiang, F., Hydrostatic Pressure Induced Transition From δTC to δℓ Pinning Mechanism in MgB2. Superconductor Science and Technology 2015, 28 (5), 055001. 20. Sun, T.; Wang, Y.; Yu, W.; Wang, Y.; Dai, Z.; Liu, Z.; Shivananju, B. N.; Zhang, Y.; Fu, K.; Shabbir, B.; Ma, W.; Li, S.; Bao, Q., Flexible Broadband Graphene Photodetectors Enhanced by Plasmonic Cu3−Xp Colloidal Nanocrystals. Small 2017, 13 (42), 1701881. 21. Shabbir, B.; Ullah, A.; Hassan, N.; Irfan, M.; Khan, N. A., Suppression of Superconductivity Due to Enhanced Co Doping in Cu0.5Tl0.5Ba2Ca2Cu3−yCoyO10−δ Superconductors. Journal of Superconductivity and Novel Magnetism 2011, 24 (5), 1521-1526. 22. Shabbir, B.; Malik, M. I.; Khan, N. A., Effect on Diamagnetism and Phonon Modes due to Mg and Be Doping at Ca Sites in Cu0.5Tl0.5Ba2Ca3−yMyCu4O12−δ(y=0 and 1.5 for M=Mg, Be) High Temperature Superconductors. Journal of Superconductivity and Novel Magnetism 2011, 24 (6), 1977-1983. 23. Chen, K.; Zhou, J.; Chen, W.; Zhong, Q.; Yang, T.; Yang, X.; Deng, C.; Liu, Y., Growth Kinetics and Mechanisms of Multinary Copper-Based Metal Sulfide Nanocrystals. Nanoscale 2017, 9 (34), 12470-12478. 24. Guc, M.; Lähderanta, E.; Shakhov, M. A.;

Page 10 of 17

Hajdeu-Chicarosh, E.; Arushanov, E.; Lisunov, K. G., Magnetotransport of Cu2ZnSnS4 Single Crystals in Two Regimes of Variable–Range Hopping Conduction. Surface Engineering and Applied Electrochemistry 2017, 53 (2), 186-195. 25. Hao, Y.; Wang, Y.; Wang, L.; Ni, Z.; Wang, Z.; Wang, R.; Koo, C. K.; Shen, Z.; Thong, J. T. L., Probing Layer Number and Stacking Order of Few-Layer Graphene by Raman Spectroscopy. Small 2010, 6 (2), 195-200. 26. Ferrari, A. C.; Meyer, J. C.; Scardaci, V.; Casiraghi, C.; Lazzeri, M.; Mauri, F.; Piscanec, S.; Jiang, D.; Novoselov, K. S.; Roth, S.; Geim, A. K., Raman Spectrum of Graphene and Graphene Layers. Physical Review Letters 2006, 97 (18), 187401. 27. Abrikosov, A. A., Quantum Magnetoresistance. Physical Review B 1998, 58 (5), 2788-2794. 28. McCann, E.; Kechedzhi, K.; Fal’ko, V. I.; Suzuura, H.; Ando, T.; Altshuler, B. L., WeakLocalization Magnetoresistance and Valley Symmetry in Graphene. Physical Review Letters 2006, 97 (14), 146805. 29. Wu, X.; Li, X.; Song, Z.; Berger, C.; de Heer, W. A., Weak Antilocalization in Epitaxial Graphene: Evidence for Chiral Electrons. Physical Review Letters 2007, 98 (13), 136801. 30. Liu, Y.; Lew, W. S.; Sun, L., Enhanced Weak Localization Effect in Few-Layer Graphene. Physical Chemistry Chemical Physics 2011, 13 (45), 20208-20214. 31. Zhang, L.; Zhang, Y.; Camacho, J.; Khodas, M.; Zaliznyak, I., The Experimental Observation of Quantum Hall Effect Of L=3 Chiral Quasiparticles in Trilayer Graphene. Nature Physics 2011, 7, 953. 32. Parish, M. M.; Littlewood, P. B., NonSaturating Magnetoresistance in Heavily Disordered Semiconductors. Nature 2003, 426, 162. 33. Narayanan, A.; Watson, M. D.; Blake, S. F.; Bruyant, N.; Drigo, L.; Chen, Y. L.; Prabhakaran, D.; Yan, B.; Felser, C.; Kong, T.; Canfield, P. C.; Coldea, A. I., Linear Magnetoresistance Caused by Mobility Fluctuations in n-Doped Cd3As2. Physical Review Letters 2015, 114 (11), 117201. 34. Hu, J.; Parish, M. M.; Rosenbaum, T. F., Nonsaturating Magnetoresistance of Inhomogeneous Conductors: Comparison of Experiment and Simulation. Physical Review B 2007, 75 (21), 214203. 35. Ramadoss, K.; Mandal, N.; Dai, X.; Wan, Z.; Zhou, Y.; Rokhinson, L.; Chen, Y. P.; Hu, J.; Ramanathan, S., Sign Reversal of Magnetoresistance in a Perovskite Nickelate by Electron Doping. Physical Review B 2016, 94 (23), 235124. 36. Li, P.; Zhang, Q.; He, X.; Ren, W.; Cheng, H.M.; Zhang, X.-x., Spatial Mobility Fluctuation Induced Giant Linear Magnetoresistance in Multilayered Graphene Foam. Physical Review B 2016, 94 (4), 045402.


Page 11 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60




Page 12 of 17


Page 13 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 1: (a) The XRD spectrum of CZTS shows three broad peaks positioning at 2Ө of 28.26⁰, 47.28⁰, 55.24⁰ corre-sponds to the (112), (220), (312) planes revealing that the as-synthesized CZTS has small crystallite size (b) Raman spectrum for few-layer GF and CZTS with prominent peaks. The peaks present in the lower wavenumber of 50-400 cm⁻1 are confirming the presence of Nanocrystals on graphene sheets with CZTS composition 35x18mm (300 x 300 DPI)



Figure 2: (a) TEM image of GF and (b) HRTEM image of GF (the inset shows the SAED pattern of GF). (c) High magnifi-cation TEM image of GF/CZTS (the inset shows SAED pat-tern of GF/CZTS) and (d) HRTEM image of GF/CZTS which clearly shows the existence of highly crystalline CZTS nano-crystals. 119x109mm (300 x 300 DPI)


Page 14 of 17

Page 15 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 3: (a-d) MR curves for GF, GF/CZTS specimens at different temperatures and fields. All curves show positive and linear MR responses and enhancement is observed for all GF/CZTS nanocrystals devices (e) MR enhancement from nearly 90% to 150% in highly concentrated GF/CZTS at 5K and 5T. (f) MR curves versus temperature for different spec-imens at 5T illustrates significant enhancement at different temperatures. 141x191mm (300 x 300 DPI)



Figure 4: (a) provides a graphical scheme for the MR meas-urements. (b) Schematic for graphene foam (c) Integration of Cu2ZnSnS4 nanocrystals and Graphene foam (d,e) shows the evolution of mobility fluctuation mechanism due to the formation of nanoboundaries, by the integration of Cu2ZnSnS4 Nanocrystals and Graphene foam. Large MR in GF/CZTS is observed due to strong mobility fluctuations. Both materials are measured by using a special homemade PPMS puck (Figure S6) in current voltage (IV) geometry.


Page 16 of 17

Page 17 of 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 5: (a) MR(%) vs B2 is plotted at different tempera-tures in order to calculate the mobility for GF/CZTS-5min. Similar method is used to obtain the mobilities for other specimens. A low field indicates parabolic drifts (due to the electron trajectory being distorted under Lorentz forces) while linear trends are realized at high fields as marked in different colour sections (b) shows mobility values at differ-ent temperatures and different specimens. An increase in mobility values are calculated in hybrid GF/CZTS devices with HC specimen being the highest.


Superior Magnetoresistance Performance of Hybrid Graphene Foam

Recommend Documents