Tuning the Ignition Performance of a Microchip Initiator by Integrating

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Tuning the Ignition Performance of a Microchip Initiator by Integrating Various Al/MoO3 Reactive Multilayer Films on a Semiconductor Bridge Jianbing Xu, Yu Tai, Chengbo Ru, Ji Dai, Yinghua Ye,* Ruiqi Shen, and Peng Zhu Department of Applied Chemistry, School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China

ABSTRACT: Reactive multilayer films (RMFs) can be integrated into semiconducting electronic structures with the use of microelectromechanical systems (MEMS) technology and represent potential applications in the advancement of microscale energy-demanding systems. In this study, aluminum/molybdenum trioxide (Al/MoO3)-based RMFs with different modulation periods were integrated on a semiconductor bridge (SCB) using a combination of an image reversal lift-off process and magnetron sputtering technology. This produced an energetic semiconductor bridge (ESCB)-chip initiator with controlled ignition performance. The effects of the Al/MoO3 RMFs with different modulation periods on ignition properties of the ESCB initiator were then systematically investigated in terms of flame duration, maximum flame area, and the reaction ratio of the RMFs. These microchip initiators achieved flame durations of 60−600 μs, maximum flame areas of 2.85−17.61 mm2, and reaction ratios of ∼14−100% (discharged with 47 μF/30 V) by simply changing the modulation periods of the Al/MoO3 RMFs. This behavior was also consistent with a one-dimensional diffusion reaction model. The microchip initiator exhibited a high level of integration and proved to have tuned ignition performance, which can potentially be used in civilian and military applications. KEYWORDS: reactive multilayer films, microelectromechanical systems, magnetron sputtering, aluminum/molybdenum trioxide, energetic semiconductor bridge

1. INTRODUCTION Reactive multilayer films (RMFs) consisting of alternating layers of two or more different materials show excellent performance in many aspects such as ignition, energy release rates, and other properties similar to energetic materials.1−3 These reactive materials can also be integrated into semiconducting electronic devices using microelectromechanical systems (MEMS) technology, which can apply into “nanoenergetics-on-a-chip” (NOC) technology.4−6 NOC has a wide range of potential applications in the field of miniature energy-demanding devices such as microignition,4,7−9 micropropulsion,10,11 micro safe and arming devices,12 and electroexplosive devices.13−15 A semiconductor bridge (SCB) is a type of advanced electropyrotechnic initiator device which is concentrated within semiconductor devices, MEMS technology, and energetic materials.16 SCBs were first invented by Hollander in 196817 but did not garner much attention until 198718 when their ignition performance was greatly improved by the Sandia National Laboratory. Since its invention, the SCB device has been used © 2017 American Chemical Society

in civilian and military applications due to its high degree of safety, rapid response time, and low energy input as well as its high level of integration19−21 compared to that of traditional electro-pyrotechnic initiators which use a bridge wire to initiate subsequent reactions. For a typical SCB, a plasma is generated by an electrical explosive reaction caused by high voltage being placed across the bridge area. The heated plasma then rapidly spreads to the charges and initiates ignition.17,22 The duration time and size of the flame accompanying the plasma both play a key role in the successful ignition of the charge. This fact has triggered extensive research into how to improve the duration time and size of the flame without increasing input energy. Indeed, researchers studied various kinds of SCBs in attempts to improve ignition performance, including single-metal film SCBs,23,24 multilayer metal film SCBs,25 and reactive multilayer film SCBs.7,26,27 However, all of the above-mentioned research Received: November 15, 2016 Accepted: January 17, 2017 Published: January 17, 2017 5580

DOI: 10.1021/acsami.6b14662 ACS Appl. Mater. Interfaces 2017, 9, 5580−5589

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ACS Applied Materials & Interfaces

in an oven for 3 min at 115 °C. Subsequently, the processed PR layer was entirely exposed to the UV radiation (no filtering was used) to solubilize the non-cross-linked region. Then, an inverted trapezoid profile was generated by dissolving the non-cross-linked region using a developer (AZ400 K), which revealed the SCB. Next, the RMFs were deposited on the prepared photoresist structure of the inverted trapezoid profile using magnetron sputtering technology. Finally, the patterned RMFs were defined by removing unnecessary portions of the deposited RMFs’ thin film in an ultrasonic bath containing acetone. As mentioned above, thermite RMF systems are a new type of nanothermite consisting of alternating nanolayers of Al and metal oxide. To obtain Al/MoO3 RMFs with different modulation periods, magnetron sputtering is used because it has the advantages of low temperature and high speed, which meet the requirements for the preparation of multiple alternating depositions on the nanometer scale and also provide accurate control over layer thickness in composite films. Figure 1c shows a magnetron sputtering setup for RMF deposition. The Al target (purity >99.999%) was direct-current (DC) sputtered at 150 W, and the MoO3 target (purity >99.999%) was radiofrequency (RF) sputtered at 200 W to maintain an optimized film quality. The base pressure of the chamber was 9 × 10−4 Pa, while the working pressure for the two types of targets was selected to be 0.4 Pa. Ultrahigh purity argon (99.99%) was employed as the working gas with a flux of 12 sccm. A rotating substrate table was employed to realize multiple alternating depositions, and a baffle switch was controlled by setting the computer program to adjust the thickness of the RMFs. The selected modulation periods in various RMFs were 50, 150, and 1500 nm at theory stoichiometric ratios, respectively, and the total thickness was 3 μm. For the convenience of identification, the ESCB initiators with different modulation periods were denoted as ESCB-50 nm, ESCB-150 nm, ESCB-1500 nm. 2.2. Characterization Methods. To investigate the electrical explosion characteristics of Al/MoO3−ESCB initiators, a capacitor (47 μF) discharge firing circuit test system was adopted to apply the current across the Al/MoO3−SCB initiator, as shown in Figure 2. In the experiment, switch A was closed first to charge the capacitor to the settled voltage. Then, switch A was disconnected, and switch B was closed. Multiple tests were performed with the charging voltage ranging from 30 to 50 V at 5 V increments. Under each identical condition, three samples of each kind of initiator were initiated, and then the results were averaged. The ignition process was recorded using a high-speed camera (HG-100 K) that captured 50 000 frames per second. At the same time, voltage and current were recorded synchronously with an oscilloscope. The surface roughness measurements of the MoO3 and Al layers were performed using atomic force microscopy (AFM, Solver P47). Structural microscopic characterization was performed using scanning electron microscopy (SEM, S-4800 II). The multilayer composition was determined using an energy dispersive spectrometer (EDS, NORAN System SIX). To examine the exothermic reaction temperatures in the various Al/MoO3 RMFs, a glass wafer (Φ 50 mm × H1 mm) was spin coated with a photoresist layer prior to deposition so that the Al/MoO3 RMFs could be easily peeled afterward by dissolving the photoresist. Then, differential scanning calorimetry (DSC, NETZSCH STA 449 C) was carried out at temperatures ranging from 30 to 900 °C under N2 flow. The activation energy of the exothermic reaction was determined with DSC experiments at heating rate from 5 to 20 °C·min −1.

focus solely on improvement of ignition performance. It will be more worthwhile to tune the ignition performance by controlling the duration time and size of the stimulated plasma to initiate charges with different sensitivity levels. Thermite RMF systems are mixtures of nano-Al films and metal oxide films such as CuO,28−30 MoO3,27,31 and NiO.32,33 The exothermic reactions of thermite RMF systems have high energy density and high adiabatic temperatures to make up for heat loss and allows thermite RMFs to maintain self-sustaining combustion at the microscale, as shown in Table 1.34 Based on Table 1. Theoretical Energy Release of Energetic Materials energetic materials

mass energy density (cal/g)

volume energy density (cal/cm3)

adiabatic temperature (K)

Al/CuO Al/MoO3 Al/Fe2O3 Al/NiO Al/Ni B/Ti

974.1 1124 945.4 822.3 330 652

4976 4297 3947 4288 1710 2560

2843 3253 3135 3187 >1910 >2452

the advantages listed above, thermite RMF systems are promising structures for integrating energetic layers onto an SCB chip, which increases the duration time and size of the flame accompanying the chemical reaction. Therefore, it is easy to tune ignition performance of the SCB−chip initiator integrated with RMFs because the reactivity of these RMFs can be easily controlled by changing the thickness of each layer and the number of layers.35 In this study, an Al/MoO3 RMF was selected because it is characterized by a reaction energy and adiabatic temperature much higher than those of other RMFs such as Al/Ni RMFs (Table 1). Three kinds of energetic semiconductor bridge (ESCB) initiators were fabricated using MEMS technology, which allowed us to create large batches of the ESCB. Tuning of the ignition performance of the ESCB initiators was systematically investigated by varying the internal structures of the Al and MoO3 multilayers accumulated on the surface of the SCB. The ignition performance of the given ESCB initiators was exhibited in terms of the flame duration, maximum flame area, and reaction ratio of the RMFs when ignited.

2. EXPERIMENTAL SECTION 2.1. Fabrication of ESCB Initiators. The SCB chips are fabricated using a conventional complementary metal oxide semiconductor (CMOS) procedure.19 More than 1000 SCB patterns can be defined on a 4 in. diameter wafer, which is then diced into individual chips. In this experiment, n-type doped polysilicon was applied to create SCB chips. Figure 1a shows a digital image of a fabricated SCB. The SCB had a heating area of a “double-V” (with the angles of 90°) shaped bridge, and the size was 380 μm (width) × 80 μm (length) × 2.5 μm (thickness). Two rectangle-shape Au/Ti electrodes with a size of 1 × 1.96 mm were adopted to connect to SCB. An image reversal lift-off process is used for the patterned RMFs because the inverted trapezoid profile of the photoresist is beneficial for fabricating thick film graphics with high accuracy. The process is illustrated schematically in Figure 1b. The SCB chip was cleaned with acetone, alcohol, and deionized water in an ultrasonic bath for 10 min. Then, the cleaned SCB chip was placed in an oven for 1.5 h at 100 °C. Next, an image reversal photoresist (PR; AZ5200NJ) was spin coated on the SCB chip substrate at 3000 rpm for 10 s and soft-baked in an oven for 2 min at 100 °C. Afterward, the PR layer was partially exposed to ultraviolet (UV) radiation with an intensity of 20 mJ/cm2 through a mask using an ultraviolet lithography system (URE_2000A). The UV-exposed region of the PR layer was cross-linked by reversal baking

3. RESULTS AND DISCUSSION 3.1. Structure and Layer Morphology of Al/MoO3 RMFs. AFM indicated a roughness of 5.03 and 5.21 nm for the MoO3 and Al thin layers, respectively, with a scan area of 10 × 10 μm, as illustrated in Figures 3a and b. EDS analysis was performed using 3 μm Al/MoO3 RMFs deposited on a native oxidized silicon substrate. The EDS patterns of Al, Mo, O, and Si (Figure 3c) confirmed the presence of each expected element in the RMFs. 5581


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Figure 1. (a) Photographs and optical microscope images of the SCB, (b) schematic representation of the MEMS-based processes used for fabricating the ESCB, and (c) the magnetron sputtering system and RMFs-deposited ESCB initiator.

Figure 2. Schematic drawing of the test circuit used to generate pulses across a sample bridge and provide data on bridge current, voltage, and the ignition process. 5582


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Figure 3. AFM images of the (a) Al and (b) MoO3 film surfaces and (c) EDS patterns on the RMFs.

Figure 4. Schematic of the various assembled RMFs on the SCB and the cross-sectional SEM images of the RMFs.

to act as an insulating layer and avoid short-circuits of the SCB of before ignition. Subsequently, Al and MoO3 layers were deposited alternately using a magnetron sputtering process.

Figure 4 shows the conceptual schematics and SEM images of the cross-sectional area of various Al/MoO3 RMFs. First, a thin layer of MoO3 (300 nm) was deposited on the bottom 5583


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80.09 kJ/mol, respectively. For Al/MoO3 RMFs with modulation period of 1500 nm, there were two endothermic peaks at 703.1 and 736.3 °C at the heating rate of 20 °C·min−1, while only one endothermic peak was seen at lower heating rates. The main endothermic peak was selected, and the activation energy was calculated at 74.99 kJ/mol. It seems that the modulation periods of Al/MoO3 had little effect on the activation energy of the exothermic reaction. 3.2. Ignition Performance for Three Kinds of ESCB Initiators. The ignition processes of ESCB-1500, ESCB-150, and ESCB-50 nm were qualitatively measured using a highspeed camera. Figure 7 shows a sequence of high-speed video frames of the burst action for SCB, ESCB-1500 nm, ESCB-150 nm, and ESCB-50 nm all discharged at 47 μF/30 V. The interval between adjoining pictures is 20 μs. The right side frames correspond to the optical microscope images after ignition. When the size of the glowing emissions and projected streaks were compared, it was evident that the height and duration time of flames significantly increased as the modulation periods decreased. This was a result of enhanced reactivity. Initially, plasma was generated at 20 μs in each initiator. After generation, the plasma became weaker because no RMFs were on the SCB. Without RMFs on the SCB, plasma can last for 60 μs. The maximum flame area was measured at 2.85 mm2. Flames did not have a long duration time or a large flame area, which indicated a low ignition performance. However, for the ESCB, the reaction of RMFs was stimulated by the generated plasma, which resulted in a combustion process with large quantities of product particles bursting forth. The reaction rates varied with the structure of the RMFs, and the duration time of the flame can reach about 600 μs for ESCB-50 nm with a maximum flame area of 17.61 mm2. Table 2 summarizes the ignition properties of SCB, ESCB-1500 nm, ESCB-150 nm, and ESCB-50 nm discharged at 47 μF/30 V, including their reaction duration, duration to maximum flame, and maximum flame height, width, and area as well as reaction ratio of the RMFs. Their ignition durations were recorded at 60, 140, 440, and 600 μs, respectively, and their maximum flame areas were measured at 2.85, 3.23, 6.52, and 17.61 mm2, respectively. In addition, the reaction ratios of various RMFs were calculated from the right side frames in Figure 7. The images clearly indicate that the reaction zones of the RMFs increased as the modulation periods decreased. Moreover, the images showed that the RMFs completely reacted for ESCB-50 nm. Therefore, ESCB-50 nm resulted in longer reaction duration time, relatively larger maximum flame area, and a higher reaction ratio. The maximum flame height for ESCB-50 nm can reach at 7.0 mm, which has a wide application in the field of noncontact ignition. The voltage and current of ESCB initiators were recorded using an oscilloscope. The second voltage peak is defined as the critical explosive temporal of the SCB because it corresponded to the emergence of plasma.20 Figure 8a shows the critical explosive energy (Ec) for each ESCB discharged with different discharge voltages. From this experiment, it was determined that discharge voltage had no effect on the Ec for ESCB with the same modulation period; however, the Ec increased with the increase in the modulation periods of the RMFs. The reason may be that the Ec was related only to the structure of the SCB, while the energy used for melting and gasifying the SCB remained consistent. Moreover, the RMFs may absorb heat from the SCB as a result of an extension of the Ec in the ESCB initiators. Furthermore, the heat conductivity of film decreased

Each modulation period was 1500 nm (Al/MoO3: 900/600 nm, 2 periods, Φ = 1), 150 nm (Al/MoO3: 90/60 nm, 20 periods, Φ = 1), and 50 nm (Al/MoO3: 20/30 nm, 60 periods, Φ = 1), receptivity, where Φ was the stoichiometric ratio. The final thickness of all of the Al/MoO3 RMFs was approximately 3 μm. The modulation period of RMFs is a crucial parameter because it significantly influences chemical reactions of Al/MoO3. Moreover, the heat flow and reaction velocity can be easily changed by controlling the modulation period of RMFs with fixed thickness at the theoretical stoichiometric ratio.28,29 Therefore, the ignition performance of the ESCB initiators can be tuned by varying the structure of the Al/MoO3 RMFs. As shown in Figure 4, the cross-sectional SEM images of the Al/MoO3 RMFs showed that the Al and MoO3 layers had distinct boundary lines for the Al/MoO3 RMFs (i.e. 1500 and 150 nm). The visible division between layers was distinct for larger modulation periods of Al/MoO3 RMFs because the layers themselves were thick, whereas the visible division between Al/MoO3 RMFs was less distinct in the case of 50 nm modulation periods of Al/MoO3 RMFs because each layer was getting thinner. DSC analysis was performed at heating rate of 20 °C·min−1 to examine the effects of the various modulation periods on the exothermic reaction temperature of the Al/MoO3 RMFs, as shown in Figure 5. The exothermic peak of RMFs with

Figure 5. DSC plots of Al/MoO3 RMFs with different modulation periods at heating rate of 20 °C·min −1.

modulation periods of 50 and 150 nm were 556.6 and 589.8 °C, respectively (as shown in the shadow area). For the thickest modulation period of Al/MoO3 RMFs (1500 nm), there were two endothermic peak at 703.1 and 736.3 °C after the melting point of Al at 660 °C (as shown in the dotted line). The exothermic peak increased as the modulation periods of the Al/MoO3 RMFs increased. This suggested that reactivity was higher for smaller modulation periods of Al/MoO3 RMFs because an increase in the interfacial contact area between the Al and MoO3 films significantly affected the chemical reactivity of the RMFs. To obtain the activation energy of the exothermic peak, the Kissinger method was used. Figure 6 shows the DSC plots of Al/MoO3 RMFs at various heating rates from 5 to 20 °C·min−1 and the fitting curves generated using the Kissinger method. The activation energy of Al/MoO3 RMFs with modulation periods of 50 and 150 nm were calculated at 75.65 and 5584


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Figure 6. DSC plots of Al/MoO3 RMFs at various heating rates and the fitting curves used for calculating activation energy of the exothermic peak by the Kissinger method. Al/MoO3 at (a) 50, (b) 150, and (c) 1500 nm (here, β is the heating rate, and Tmax is the temperature of the exothermic peak).

with thickness,36−38 which explained the minimum Ec for the thinnest films (ESCB-50 nm) among various ESCB initiators because of lower loss of heat in the RMFs (50 nm). Figure 8b shows the duration time (tl) of flame after ignition for various ESCB initiators. For SCB, the tl only reached about 100 μs, while the tl can reach about 400 and 600 μs for ESCB-150 and

ESCB-50 nm, respectively, with discharge voltages from 30 to 50 V. The ESCB-1500 nm had tl from 150 to 400 μs with discharge voltages from 30 to 50 V. This suggested that the ignition performance of the ESCB microchip initiators can be easily controlled by designing the accumulation structures of the Al/MoO3 RMFs. 5585


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Figure 7. Ignition processes of the SCB and various ESCB initiators and their microscope images after ignition. (a) SCB, (b) ESCB-1500 nm, (c) ESCB-150 nm, and (d)ESCB-50 nm.

Table 2. Ignition Properties of the SCB and Various ESCB Initiators Discharged at 47 μF/30 V initiator

ignition duration (μs)

time to maximum flame (μs)

maximum flame height (mm)

maximum flame width (mm)

maximum flame area (mm2)

reaction ratio (%)

SCB ESCB-1500 nm ESCB-150 nm ESCB-50 nm

60 140 440 600

20 40 120 140

1.9 2.4 3.6 7.0

1.7 1.4 2.3 4.8

2.85 3.23 6.52 17.61

14 22 100

Q̇ rxn = nAΔHrnxJ

3.3. Ignition Model for RMFs. On the basis of the above results, the RMFs’ modulation period has a direct effect on the ignition process. A one-dimensional diffusion reaction model39 was proposed to study the effect of the number of interfaces of RMFs on the reaction ignition (Figure 9). The Al/MoO3 RMFs was ignited by the generated plasma, as shown in Figure 9a. The interface of Al/MoO3 was assumed to dominate the reactivity and oxygen atoms diffused from the MoO3 layer to the Al layer through the interface, as shown in Figure 9b. The analysis energy conservation equation with the equation of state of ideal conditions

dT 1 ̇ = Q dt Cp rxn

(2) 2

where n is the number of interfaces, A (m ) is the surface area of each interface, ΔHrxn (J/mol) is the energy released from each mol of reaction, and J (mol/(s·m2)) is the flux of oxygen through each interface. A can be calculated based on the heat area of SCB with 380 × 80 μm2. The number of interfaces is related to the number of modulation periods (N) of RMFs through n = 2N − 1. Eq 3 is the Fickian diffusion flux through each interface

J=−

∂C D0e(−Ea / RT ) ∂x

(3)

where ∂C (mol/m4) is the concentration gradient across the ∂x interface, D0 is the pre-exponential to the diffusivity, and Ea is its activation energy. The concentration gradient is based on O atoms going from zero to the concentration in MoO3 over the length of a typical interfacial barrier layer (3−5 nm29) to be

(1)

relates the temporal change in temperature to the rate of heat generation by reaction (Q̇ rxn) divided by the heat capacity (Cp). The heat generated is evaluated in eq 2 5586


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Egan39 calculated the ignition temperature of thermite nanolaminates with the value (Ea = 20 kJ/mol, D0 = 9.0 × 10−13 m2/s) first, and the final result of the iterative refinement was obtained with the value (Ea = 49 kJ/mol, D0= 2.9 × 10−10m2/s). The Ea of Al/MoO3 RMFs with modulation periods of 50, 150, and 1500 nm in this experiment were measured at 75.65, 80.09, and 74.99 kJ/mol, respectively. The average Ea = 76.91 kJ/mol and D0 = 2.9 × 10−10 m2/s were selected to calculate the ignition temperature. The modeled ignition temperature is shown in Figure 10.

Figure 10. Relationship of modeled ignition temperature with number of modulation periods.

Figure 8. Critical explosive energy (a) and ignition duration (b) of SCB, ESCB-1500 nm, ESCB-150 nm, ESCB-50 nm at different discharge voltages (here, Ec is the critical explosive energy and tl is ignition duration).

When N is in the range of 0−15, the ignition temperature of RMFs decreased rapidly with the amplitude of the number of modulation periods, while the ignition temperature of RMFs decreased slowly when N is in the range of 15−60. This result clearly indicates the change of chemical reactivity with different modulation periods of the RMFs, which is consistent with the change of ignition performance for various ESCB initiators.

4. CONCLUSIONS In this study, three kinds of ESCB−chip initiators (ESCB-1500, ESCB-150, and ESCB-50 nm) were proposed by depositing Al/MoO3 RMFs with different modulation periods (1500, 150, and 50 nm) on a SCB. The ESCB−chip initiators were fabricated using a combination of MEMS-based processes with image reversal lift-off and magnetron sputtering technology. The as-deposited Al/MoO3 RMFs with different modulation periods were identified by SEM and DSC. SEM showed the distinct layer structure for the Al/MoO3 RMFs (i.e. 1500 and 150 nm), while a less distinct layer was seen in the case of smaller modulation periods of Al/MoO3 RMFs (i.e. 50 nm). The main exothermic peak of RMFs with modulation periods of 50, 150, 1500 nm were 556.6, 589.8, and 736.3 °C, respectively, at the heating rate of 20 °C/min. The ESCB−chip initiators can produce fierce flames when a voltage was supplied to the SCB. The ignition durations of the SCB, ESCB-1500 nm, ESCB-150 nm, and ESCB-50 nm were recorded at 60, 140, 440, and 600 μs, respectively, and their maximum flame areas were measured at 2.85, 3.23, 6.52, and 17.61 mm2, respectively, both discharged at 47 μF/30 V. Furthermore, this behavior is consistent with a one-dimensional diffusion reaction model. In short, the ESCB−chip initiator detailed in this report exhibited controlled ignition performance and can potentially be

Figure 9. Schematic of ignition model for RMFs. (a) Ignition process of Al/MoO3 RMFs, (b) diffusion reaction at the interface of Al/MoO3, and (c) concentration gradient at the interface of Al/MoO3.

8.14 × 1012 mol/m4, as shown in Figure 9c. The electricalexplosive process of SCB was achieved in ∼10−100 μs and produced high temperature plasma at about 3000 K. As such, the film temperature rapidly increased above that of the plasma. dT 103 K = = 108 ∼ 109 K/s dt 10 × 10−6 s ∼ 100 × 10−6 s (4)

For this reason, the ignition temperature (Tign) is defined as the point at which the temperature rise from reaction (eq 1) exceeds the heating rate from the plasma (108 ∼ 109 K/s). Combining eqs 1−3 and solving for ignition temperature gives Tign

−1 ⎧ ⎡ 8 9 ⎤⎫ −Ea ⎪ ⎢ (10 ∼ 10 K/s)Cp ⎥⎪ ⎨ln ⎬ = R ⎪ ⎢⎣ nAΔHrnx ∂C D0 ⎥⎦⎪ ⎩ ⎭ ∂x

(5) 5587


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(15) Zhang, D.; Xiang, Q.; Li, X. Highly Reactive Al-Cr2O3 coating for Electric-Explosion Applications. RSC Adv. 2016, 6, 100790− 100795. (16) Headley, P. S. A Semiconductor Bridge (SCB) Primary Explosive Detonator; Sandia National Laboratories: Albuquerque, NM, 1986. (17) Hollander, Jr.; Lewis, E. Semiconductive Explosive Igniter. U.S. Patent US3,366,055, January 30, 1968. (18) Bickes, Jr., R. W.; Schwarz, A. C. Semiconductor Bridge (SCB) Igniter. U.S. Patent US4,708,060, November 24, 1987. (19) Benson, D. A.; Larsen, M. E.; Renlund, A. M.; Trott, W. M.; Bickes, R. W., Jr. Semiconductor Bridge: a Plasma Generator for the Ignition of Explosives. J. Appl. Phys. 1987, 62, 1622−32. (20) Lee, K. N.; Park, M. I.; Choi, S. H.; Park, C. O.; Uhm, H. S. Characteristics of Plasma Generated by Polysilicon Semiconductor Bridge (SCB). Sens. Actuators, A 2002, 96, 252−257. (21) Li, H.; Zhou, Q.; Ren, H.; Jiao, Q.; Du, S.; Yang, G. Ignition Characteristics of Semiconductor Bridge Based on Lead Styphnate and Lead Azide Charges Under Capacitor Discharge Conditions. Sens. Actuators, A 2016, 241, 27−33. (22) Jongdae, K.; Kee-Soo, N.; Jungling, K. C. Plasma Electron Density Generated by a Semiconductor Bridge as a Function of Input Energy and Land Material. IEEE Trans. Electron Devices 1997, 44, 1022−1026. (23) Benson, D. A.; Bickes, Jr., R. W.; Blewer, R. S. Tungsten Bridge for the Low Energy Ignition of Explosive and Energetic Materials. U.S. Patent US4,976,200, December 11, 1990. (24) Martinez-Tovar, B.; Foster, M. Titanium Semiconductor Bridge Igniter. U.S. Patent Application US11/829,526, July 27, 2007. (25) Martinez-Tovar, B.; Montoya, J. A. Semiconductor Bridge Device and Method of Making the Same. U.S. Patent US6,133,146, October 17, 2000. (26) Mueller-Fiedler, R.; Bernhard, W.; Kunz, U. Bridge Igniter. U.S. Patent US 6,810,815, November 2, 2004. (27) Zhu, P.; Jiao, J. S.; Shen, R. Q.; Ye, Y. H.; Fu, S.; Li, D. L. Energetic Semiconductor Bridge Device Incorporating Al/MoOx Multilayer Nanofilms and Negative Temperature Coefficient Thermistor Chip. J. Appl. Phys. 2014, 115, 194502. (28) Petrantoni, M.; Rossi, C.; Salvagnac, L.; Conedera, V.; Esteve, A.; Tenailleau, C.; Alphonse, P.; Chabal, Y. J. Multilayered Al/CuO Thermite Formation by Reactive Magnetron Sputtering: Nano versus Micro. J. Appl. Phys. 2010, 108, 084323. (29) Bahrami, M.; Taton, G.; Conedera, V.; Salvagnac, L.; Tenailleau, C.; Alphonse, P.; Rossi, C. Magnetron Sputtered Al-CuO Nanolaminates: Effect of Stoichiometry and Layers Thickness on Energy Release and Burning Rate. Propellants, Explos., Pyrotech. 2014, 39, 365−373. (30) Amini-Manesh, N.; Basu, S.; Kumar, R. Modeling of a Reacting Nanofilm on a Composite Substrate. Energy 2011, 36, 1688−1697. (31) Fu, S.; Zhu, Y.; Li, D.; Zhu, P.; Hu, B.; Ye, Y. H.; Shen, R. Deposition and Characterization of Highly Energetic Al/MoOx Multilayer Nano-Films. Eur. Phys. J.: Appl. Phys. 2013, 64, 30301. (32) Yan, Y. C.; Shi, W.; Jiang, H. C.; Xiong, J.; Zhang, W. L.; Li, Y. R. Fabrication and Characterization of Al/NiO Energetic Nanomultilayers. J. Nanomater. 2015, 2015, 1−6. (33) Yan, Y.; Shi, W.; Jiang, H.; Xiong, J.; Zhang, W.; Li, Y. Characteristics of the Energetic Igniters Through Integrating Al/NiO Nanolaminates on Cr Film Bridge. Nanoscale Res. Lett. 2015, 10, 1−7. (34) Fischer, S. H.; Grubelich, M. C. Theoretical Energy Release of Thermites, Intermetallics, and Combustible Metals. Proceedings of the 24th International Pyrotechnics Seminar; Monterey, CA, July 27−31, 1998. (35) Marin, L.; Nanayakkara, C. E.; Veyan, J. F.; Warot-Fonrose, B.; Joulie, S.; Esteve, A.; Tenailleau, C.; Chabal, Y. J.; Rossi, C. Enhancing the Reactivity of Al/CuO Nanolaminates by Cu Incorporation at the Interfaces. ACS Appl. Mater. Interfaces 2015, 7, 11713−11718. (36) Lukes, J. R.; Li, D. Y.; Liang, X. G.; Tien, C. L. Molecular Dynamics Study of Solid Thin-Film Thermal Conductivity. J. Heat Transfer 2000, 122, 536−543.

used in civilian and military applications, especially in noncontact ignition such as air bags in automobiles, micropropulsion systems, and many ordnance systems.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Jianbing Xu: 0000-0001-6394-2589 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation (Grant U1230115) and the Ordinary University Graduate Student Scientific Research Innovation Projects of Jiangsu Province (Grant KYLX15_0351).

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REFERENCES

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Tuning the Ignition Performance of a Microchip Initiator by Integrating

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