Doping Induced Polymorph and Carrier Polarity Changes in LaSeF

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Doping induced polymorph and carrier polarity changes in LaSeF Takeshi Arai, Soshi Iimura, and Hideo Hosono Chem. Mater., Just Accepted Manuscript • DOI: 10.1021/acs.chemmater.7b05161 • Publication Date (Web): 15 Jan 2018 Downloaded from http://pubs.acs.org on January 15, 2018

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Chemistry of Materials

Doping induced polymorph and carrier polarity changes in LaSeF Takeshi Arai1, Soshi Iimura1,*, and Hideo Hosono1,2,* 1

Laboratory for Materials and Structures, Tokyo Institute of Technology, Yokohama 226-8503, Japan, 2Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama 226-8503, Japan

ABSTRACT: We identified a polymorphic change between tetragonal and hexagonal phases, accompanying a major carrier switch induced by doping of LaSeF. The hexagonal phase exhibits p-type conduction when Ca is doped into La sites. Cl doping into Se sites stabilizes the tetragonal phase and n-type conduction is realized. Successful p-type doping in the hexagonal phase and n-type doping in the tetragonal phase are explained by the energy alignment of the location of valence band maximum and conduction band minimum. We clarify the importance of orbital symmetry in controlling the band edge in different polymorphs.

Carrier doping and control of carrier polarity are key technical issues in the creation of novel semiconductors. Wide bandgap semiconductors are in demand for applications in power electronics and optoelectronics1,2,3,4. Oxide semiconductors generally show n-type conduction, whereas p-type materials are limited owing to the deep valence band maximum (VBM) arising from the high electronegativity of oxygen5,6,7. Post-transition metals (pTM) have been widely used to realize p-type conduction because the interaction of occupied Cu1+ 3d and Sn2+ 5s orbitals with oxygen 2p orbitals increases the VBM8,9,10,11,12. However, control of carrier polarity, which is required for the realization of bipolar semiconductors, is a major challenge for wide gap semiconductors. The ease of carrier doping is primarily determined by the carrier stability, i.e., a larger electron affinity (ECBM − Evac) and smaller ionization potential (EVBM − Evac) make electron and hole-doping easier, respectively, where ECBM, EVBM, and Evac are energies of conduction band minimum (CBM), VBM and vacuum level, respectively13,14,15. Hence, wide bandgap materials are inappropriate in general as candidate materials for bipolar semiconductors, as represented by Si and Ge. Although considerable efforts have been devoted to realizing transparent bipolar semiconductors, few practically applicable materials have been reported to date16,17,18. In a preceding paper, we reported a design concept for wide bandgap bipolar semiconductors based on early transition metal (eTM) cations and demonstrated its effectiveness by finding the bipolarity of tetragonal ZrOS experimentally19. Our idea was based on controlling certain features including: (i) ECBM through the symmetry of relevant orbitals that contribute to the CBM; (ii) EVBM by selection of candidate materials with short anion-anion separation; and (iii) transparency based on a forbidden band edge transition. In this paper we report LaSeF, which exhibits a wide gap and unique semiconducting properties associated with its polymorphs. This material has two polymorphs, namely hexagonal and tetragonal phases. The former shows p-type conduction; however, no n-type doping was attained. However, 1%-chlorine doping into the hexagonal phase results in a polymorphic change to the tetragonal phase, and the carrier polarity simultaneously switches from p

to n-type. The alternation of the carrier polarity and polymorph can be rationally understood as a consequence of the difference in the orbital configuration at the CBM. Namely, the shallower CBM in the hexagonal phase features the π-type La-5dz2 bonding state, which has low orbital overlap. The deeper CBM in the tetragonal phase features the σ-type La5dx2−y2 bonding state. These results indicate the importance of chemical bonding at band edge states for achieving wide-gap bipolar conduction in eTM-based semiconductors. Figures 1a and 1b show the crystal structures of hexagonal (hexa-) and tetragonal (tetra-) LaSeF, whose structure types are ZrBeSi (P63/mmc) and PbClF (P4/nmm), respectively. In both structures, the coordination number around La3+ is 9. In the hexagonal phase, the honeycomb [LaF]2+ layer is separated by the larger Se2− anions. In the tetragonal phase, a PbO-type [LaF]2+ layer is sandwiched by the Se2−. The structure map of ternary mixed anion rare-earth compounds is summarized in Table S1. One can see that tetragonal PbClF-type structure crystallizes when the ionic radii of one anion is much larger than that of the other anion. In this map, five different structure types appear at the boundary of the PbClF-type region, i.e., PbCl2, SmSI, YSF, YSeF, and ZrBeSi-type. We calculated the internal energy difference between those and the PbClF structures, and found a small energy difference in the case of LaSeF (PbClF vs ZrBeSi) and LaTeCl (PbClF vs PbCl2), indicating that these crystal structures could easily transform into each other (See Table S2 in Supporting Information). Figures 1c and 1d show band structures of the hexa- and tetra-phases, respectively. The calculated band gaps of the hexa- and tetraphases were notably different at 1.73 and 1.03 eV, respectively. Note that the calculated band gaps are likely to under estimate the experimental values because we used a local density approximation (LDA) functional. Symmetry analysis20 revealed the band gap of the hexa-phase at the Γ point is a direct-allowed type (from Γ2− to Γ1+), while that of the tetraphase is a forbidden-type (from Γ5− to Γ4−). The EVBM consists of Se-4p orbitals, while the ECBM is composed of La-5d orbitals. The hole effective mass for the hexa-phase is ~0.24 m0 along the Γ-A line and ~0.83 m0 along Γ-K, while the

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Figure 1: Crystal and band structures of hexagonal and tetragonal LaSeF. a, b Crystal structures of the hexa- (a) and tetraphases (b). Red, blue, and green spheres represent La, Se, and F atoms, respectively. c, d Band structures of the hexa- (c) and tetraphases (d). Red, blue, and green colors denote the character of the bands by projections of the wave function on the La-5d, Se-4p and F-2p Wannier orbitals as shown by the triangle color bar in between Fig. 1c and 1d. The black open circles and squares in the band structure indicate the bonding and anti-bonding states, respectively, based on La-5dz2 orbitals for the hexa-phase and La5dx2−y2 orbitals for the tetra-phase. electron effective mass is ~0.30 m0 along the Γ-A line and materials, though the Hall voltage gives the reverse sign in ~0.37 m0 along Γ-K. The mass of holes in the tetra-phase is many cases22. It is evident that the sign of the Seebeck coeffirelatively heavy, at ~0.99 m0 along the Γ-M and ~4.35 m0 cient S at room temperature changes from positive in the Cadoped hexa-phase to negative in the Cl-doped tetra-phase. along Γ-Z. The electron effective mass is similar, ~0.30 m0 Figures 3b and c summarize the doping dependence of S and along the Γ-M line and ~0.97 m0 along Γ-Z line. the electrical conductivity at 300 K, respectively. The nonFigures 2a and 2b show X-ray diffraction (XRD) pattern of doped sample exhibited high resistivity ~109 Ω cm. For the non-doped sample and analyzed Ca-content by electron probe Ca-doped sample, the conductivity was enhanced to over 10-2 micro analyzer (EPMA), respectively. The diffraction patterns S cm−1 at a Ca content of 3%. The Cl-doped tetra-phase of the un-doped and Ca-doped samples were indexed as a hexshowed a much higher conductivity than that of the Ca-doped agonal lattice. As the nominal Ca content increased, the anahexa-phase. lyzed Ca content in the LaSeF grains monotonically increased to ~2%, and then remained at a constant value of > 2%. SimiHere, we discuss the origin of the carrier polarity switch inlarly, the lattice constant, c, decreased as the Ca-content was duced by the polymorphic change associated with Cl doping increased to 2% (Fig. 2c), indicating that the Ca solubility into the hexa-phase. Figure 4a shows the density of states limit is located at approximately 2%. Hereafter, we use the (DOS) of the hexa- and tetra-phases, where the energy is nominal content for simplicity. The diffuse reflection spectra aligned at the La-5s levels located approximately 32−33 eV of the non-doped and 1%-Ca doped samples showed steep below their VBM. We found that the ECBM of the tetra-phase is absorption jumps at 2.89 and 2.91 eV, respectively. This obdeeper and that the VBM is shallower compared with those of servation is consistent with the allowed transition nature of the the hexa-phase. The difference of the CBM between the two hexa-phase. Unlike the Ca-doped samples, 1%-Cl doping conpolymorphs is attributed to the chemical bonding states besiderably changed the XRD pattern, as shown in Fig. 2e, tween the La 5d-orbitals. The electron density distributions at which is indexed as a tetragonal PbClF-type structure. The the CBM of the hexa- and tetra-phases are shown in Figs. 4b analyzed Cl content linearly increased with the nominal Cl and c, respectively. In the hexa-phase, a La-5dz2 orbital pointcontent (Fig. 2f), and the lattice constants decreased (Fig. 2g). ing along the c axis mainly contributes to the CBM state and The decrease of lattice constant indicates substitution of Cl for the lobe is parallel to the neighboring 5dz2 orbital in the nearest Se sites, rather than F sites, because the ionic radius21 of Cl unit cell, in a similar arrangement to a π-bonding interaction. (1.8Å) is larger than that of F (1.3) but smaller than that of Se In the tetra-phase the 5dx2−y2 orbitals point toward each other in (2.0). The absorption of the Cl-doped sample begins gently at a σ-bonding arrangement. a lower energy of hν = 2.2 eV, which is also consistent with In Figs. 4c and d, the corresponding bonding and antithe nature of the forbidden optical transition at the Γ point. bonding states are shown for the hexa- and tetra-phases reFigure 3a shows the results of typical thermopower measspectively. Because the multiplicity of each atomic site in urements on the polycrystalline bulk Ca-doped hexa- and ClLaSeF is two, there are two configurations of the La-5d ordoped tetra-phases. Thermopower is a reliable physical quantibital, i.e., in-phase and out-of-phase configurations. The orty for determining the carrier polarity, particularly for disorbital configuration and corresponding band structure of Ladered materials, such as polycrystalline bulk and amorphous 5dz2 orbital are the same as the


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Chemistry of Materials

Figure 2: Structural, chemical, and optical properties of polycrystalline LaSeF. a, e XRD patterns of non-doped hexa-phase (a) and Cl1%-doped tetra-phase (e). Black symbols and red/blue solid line represent the experimental data and Rietveld fitting patterns, respectively. The black tick marks below the patterns indicate the peak positions of the hexa- and tetra-phases. b, f Relationship between nominal and analyzed content of Ca in hexa-phase (b) and Cl in tetra-phase (f). The black dashed line denotes the ideal line calculated assuming the nominal content is equal to the analyzed content. c, g Doping dependence of lattice constants. Filled and open symbols denote a- and c-axis lengths, respectively. d, h Absorption spectra of the hexa- (d) and tetra-phases (h) derived from diffuse reflectance spectra at 300 K and the Kubelka−Munk relation, where α, s, and hν are the absorption coefficient, scattering factor, and photon energy, respectively. The vertical axis for direct allowed transition and direct forbidden transition are (hvα/s)2 and (hvα/s)2/3, respectively. The black dashed lines are a guide for the eyes. π and π* bonding of C-2pz in graphene23,24. The in-phase configuration of the La-5dz2 orbital at the Γ point forms a bonding state, which has its lowest energy in the La-5dz2 orbital-based bands. The out-of-phase configuration at the Γ point corresponds to the anti-bonding state, which has the highest energy because the phase of the La-5dz2 orbital is inverted with respect to both the nearest (4.22Å) and next nearest neighbor (4.76Å) La-sites. The CBM of the tetragonal phase is composed of out-of-phase La-5dx2−y2 orbitals, in which the nearest neighbor 5dx2−y2 orbitals (4.14Å) form σ-bonding interactions, while the next nearest neighbor 5dx2−y2 (4.28Å) takes a πbonding configuration. The highest energy configuration of La-5dx2−y2 appears at the M point, where both the in-phase and out-of-phase configurations form a σ-anti-bonding state (σ*) Figure 3: Transport properties of LaSeF. a Results of and those energy levels are degenerate. The corresponding thermopower measurements for Ca-doped hexa- (upper) and eigenvalues, E(k), of the bonding and anti-bonding states are Cl-doped tetra-phases (bottom). The dashed line indicates indicated by open circles and squares, respectively, in Fig. 1c linear fitting results. b Doping dependence of the Seebeck for the hexagonal and Fig. 1d for the tetragonal phase. Owing coefficient at T = 300 K. c Doping dependence of conductivity to the lower orbital overlap for the π-like configuration25, the at T = 300 K. The solid line is a guide for the eyes. band width of the La-5dz2 orbitals in the hexa-phase is only ~2 eV, which is narrower than the σ band derived from the Laand found a similar stabilization of the tetra-phase without 5dx2−y2 in the tetra-phase. electron-doping. This result clarified that the positive pressure effect was the main reason for the phase transition in the preNext we discuss the origin of the structural change from the sent case. hexa- to tetra-phase upon Cl-doping. Cl substitution into Se sites could have two possible effects on the electronic and Finally, the concepts obtained from the present findings are crystal structures of the hexa-phase; chemical pressure derived summarized in Fig. 5. The formation of bonding and antibondfrom the difference of the ionic radius and electron doping into ing states between cations and anions is responsible for the the conduction band. According to the structural map shown in band gap in ionic semiconductors and insulators (Fig. 5a)26. Table S1, a positive chemical pressure, such as that introHowever, if hybridization of the relevant orbitals in cations duced by substitution of smaller Cl− ions into larger Se2− ion and anions is forbidden by symmetry at a specific k point, the sites, would lead to a structural change of the tetragonal cation-cation bonding and anion-anion antibonding states are PbClF-type structure. Electron doping into the deeper CBM of the main contributor to ECBM and EVBM27,28, respectively, as the tetra-phase is energetically more favorable than into the shown in Figs. 5b and c. According to the irreducible represhallower CBM of the hexa-phase. We examined substitution sentation of La-5d, Se-4p, and F-2p at the Γ point (see Table 2− − 2− with 1% S , which has almost the same size as Cl , into Se S3 and S4 in Supporting Information), we found that sites of the hexa-phase



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Figure 4: Comparison of electronic structures and chemical states of hexagonal and tetragonal phases. a DOS of hexa(left) and tetra-phases (right). The vertical axis is aligned by the La-5s levels located approximately 32−33 eV below their VBM. b Electron density mapping at the CBM state of hexa- (left) and tetra-phases (right). Although the two La atoms in the unit cell are crystallographically identical, here we denote the La atom at z 0.75−0.80 as La1 and that at 0.20−0.25 as La2 for clarity. c, d Orbital configuration of bonding and anti-bonding states of La-5dz2 in the hexa-phase (c) and La-5dx2−y2 for the tetra-phase (d). The black dashed line denotes the unit cell. The orbital in the La2 site is drawn smaller to differentiate it from the orbital in the La1 site. The cross sign in right panel of Fig.4d indicates non-bonding states because La-5d x2−y2 orbitals at this site cannot form any bonding or anti-bonding states with neighboring orbitals.

Figure 5: Schematic molecular orbital diagram of conventional ionic semiconductors and the LaSeF polymorphs. a Molecular orbital diagram for semiconductors with less covalency. b, c Molecular orbital diagram for the hexa- (b) and tetra-phases (c). Owing to the poor orbital overlap between cation1 and cation2 in the hexa-phase, the CBM position is shallower than that of the tetra-phase and the situation reverses for the VBM. The red and blue allows represent the degree of orbital overlap between cationcation enlarging the conduction band width and between anion-anion enlarging the valence band width, respectively. the La 5dz2 and Se 4pz orbitals in the hexa-phase can interact fore, proper choice of parent materials is the key to achieving only with themselves but cannot achieve bonding and antiwide-gap bipolar conduction in eTM-based semiconductors. bonding states with other anion p and La 5d orbitals at the Γ In conclusion, we examined structural and chemical bondpoint. Therefore, the bonding state between the La 5dz2 orbiting effects on the electronic structure, transport and optical als and the anti-bonding state between Se 4pz orbitals constiproperties of hexagonal and tetragonal LaSeF. We found that tute the CBM and the VBM, respectively. Thus, the energy the Ca substitution for La sites of the hexagonal phase was levels simply depend on the orbital overlap between the La effective for obtaining p-type conduction, and 1-mol% Cl sub5dz2-orbitals or Se 4pz-orbitals. Alternatively, the CBM in the stitution at Se sites induced a structural change from the hextetra-phase is composed of La 5dx2−y2 and the VBM state is agonal to tetragonal phase. Inversion of carrier polarity from composed of the Se 4px/y and La 5dxz/yz orbitals. Because the p-type in the Ca-doped hexagonal phase to n-type in the ClCBM of eTM-based semiconductors is composed of cation d doped tetragonal phase was confirmed by Seebeck coefficient orbitals, the crystal structure and orbital configuration have a measurements, and the band gap of the hexagonal phase also more notable effect on the energy level of the CBM than those changed considerably from 2.9 to 2.2 eV for the tetragonal effects on pTM semiconductors, for which the CBM usually phase. The conductivity changed from 10−9 S cm−1 for the nonconsists of spherical s-orbitals of the metal29. This effect is doped hexa-phase to over 10−2 S cm−1 for both the Ca-d and clearly demonstrated by the shallower CBM formed from πCl-doped samples. Band structure calculations revealed the type La-5dz2 bonding in the hexa-phase and the deeper CBM tetragonal phase has a deeper CBM than that of the hexagonal from the σ-type La-5dx2−y2 bonding in the tetra-phase. There-


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Chemistry of Materials phase, which is consistent with the experimental finding of ntype conduction in the tetragonal phase. From the chemical bonding analysis, we concluded that the change of the carrier polarity and reduction of the band gap can be attributed to differences in the orbital configuration at the CBM. Namely, the shallower CBM in the hexagonal phase is based on the πtype La-5dz2 bonding state with low orbital overlap and the deeper CBM is related to the σ-type La-5dx2−y2 bonding state in the tetragonal phase. These results demonstrated that the proper choice of chemical bonding at the band edge state is key to achieving wide-gap bipolar conduction in eTM-based semiconductors.

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ASSOCIATED CONTENT Supporting Information. The Supporting Information is available free of charge on the ACS Publications website. The descriptions of experimental procedure, structure map, the irreducible representations, and non-bonding state. (PDF file)

AUTHOR INFORMATION

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Corresponding Author *S. I, e-mail: [email protected] *H. H, e-mail: [email protected]

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Notes Any additional relevant notes should be placed here.

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ACKNOWLEDGMENT This work was supported by the MEXT Elements Strategy Initiative to Form Core Research Center. We are grateful to Mr. Y. Kondo for EPMA measurement.

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ABBREVIATIONS

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CCR2, CC chemokine receptor 2; CCL2, CC chemokine ligand 2; CCR5, CC chemokine receptor 5; TLC, thin layer chromatography.

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REFERENCES (1)

(2)

(3) (4) (5) (6)

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Morkoç, H.; Strite, S.; Gao, G. B.; Lin, M. E.; Sverdlov, B.; Burns, M. Large‐band‐gap SiC, III‐V Nitride, and II‐VI ZnSe‐based Semiconductor Device Technologies. J. Appl. Phys. 1994, 76 (3), 1363–1398. Baliga, B. J. Power Semiconductor Device Figure of Merit for High-Frequency Applications. IEEE Electron Device Lett. 1989, 10 (10), 455–457. Yu, X.; Marks, T. J.; Facchetti, A. Metal Oxides for Optoelectronic Applications. Nat. Mater. 2016, 15 (4), 383–396. Ginley, D. S.; Bright, C. Transparent Conducting Oxides. MRS Bull. 2000, 25 (8), 15–18. Minami, T. New N-Type Transparent Conducting Oxides. MRS Bull. 2000, 25 (8), 38–44. Nomura, K.; Ohta, H.; Takagi, A.; Kamiya, T.; Hirano, M.; Hosono, H. Room-Temperature Fabrication of Transparent Flexible Thin-Film Transistors Using Amorphous Oxide Semiconductors. Nature 2004, 432 (7016), 488. Hoel, C. A.; Mason, T. O.; Gaillard, J.-F.; Poeppelmeier, K. R. Transparent Conducting Oxides in the ZnO-In2O3-SnO2 System. Chem. Mater. 2010, 22 (12), 3569–3579. Kawazoe, H.; Yasukawa, M.; Hyodo, H.; Kurita, M.; Yanagi, H.; Hosono, H. P-Type Electrical Conduction in Transparent Thin Films of CuAlO2. Nature 1997, 389 (6654), 939–942. Nagarajan, R.; Draeseke, A. D.; Sleight, A. W.; Tate, J. PType Conductivity in CuCr1−xMgxO2 Films and Powders. J. Appl. Phys. 2001, 89 (12), 8022–8025.

(24)

(25) (26)

(27)

(28)

(29)

Zakutayev, A.; Caskey, C. M.; Fioretti, A. N.; Ginley, D. S.; Vidal, J.; Stevanovic, V.; Tea, E.; Lany, S. Defect Tolerant Semiconductors for Solar Energy Conversion. J. Phys. Chem. Lett. 2014, 5 (7), 1117–1125. Walsh, A.; Watson, G. W. Influence of the Anion on Lone Pair Formation in Sn(II) Monochalcogenides: A DFT Study. J. Phys. Chem. B 2005, 109 (40), 18868–18875. Ogo, Y.; Hiramatsu, H.; Nomura, K.; Yanagi, H.; Kamiya, T.; Hirano, M.; Hosono, H. P-Channel Thin-Film Transistor Using p-Type Oxide Semiconductor, SnO. Appl. Phys. Lett. 2008, 93 (3), 032113. Zunger, A. Practical Doping Principles. Appl. Phys. Lett. 2003, 83 (1), 57–59. Hosono, H. Exploring Electro-Active Functionality of Transparent Oxide Materials. Jpn. J. Appl. Phys. 2013, 52 (9R), 090001. Robertson, J. Band Offsets, Schottky Barrier Heights, and Their Effects on Electronic Devices. J. Vac. Sci. Technol. Vac. Surf. Films 2013, 31 (5), 050821. Hosono, H.; Ogo, Y.; Yanagi, H.; Kamiya, T. Bipolar Conduction in SnO Thin Films. Electrochem. Solid-State Lett. 2011, 14 (1), H13–H16. Yanagi, H.; Hase, T.; Ibuki, S.; Ueda, K.; Hosono, H. Bipolarity in Electrical Conduction of Transparent Oxide Semiconductor CuInO2 with Delafossite Structure. Appl. Phys. Lett. 2001, 78 (11), 1583–1585. Nakamura, S.; Mukai, T.; Senoh, M. High-Power GaN P-N Junction Blue-Light-Emitting Diodes. Jpn. J. Appl. Phys. 1991, 30 (12A), L1998. Arai, T.; Iimura, S.; Kim, J.; Toda, Y.; Ueda, S.; Hosono, H. Chemical Design and Example of Transparent Bipolar Semiconductors. J. Am. Chem. Soc. 2017, 139 (47), 17175– 17180. Dresselhaus, M. S.; Dresselhaus, G.; Jorio, A. Group Theory: Application to the Physics of Condensed Matter; Springer Science & Business Media, 2007. Shannon, R. D. Revised Effective Ionic Radii and Systematic Studies of Interatomic Distances in Halides and Chalcogenides. Acta Crystallogr. A 1976, 32 (5), 751–767. Elliott, S. R. Physics of Amorphous Materials; Longman: London, 1984. DiVincenzo, D. P.; Mele, E. J. Self-Consistent EffectiveMass Theory for Intralayer Screening in Graphite Intercalation Compounds. Phys. Rev. B 1984, 29 (4), 1685–1694. Ohta, T.; Bostwick, A.; Seyller, T.; Horn, K.; Rotenberg, E. Controlling the Electronic Structure of Bilayer Graphene. Science 2006, 313 (5789), 951–954. Hoffmann, R. How Chemistry and Physics Meet in the Solid State. Angew. Chem. Int. Ed. Engl. 1987, 26 (9), 846–878. Kamiya, T.; Hosono, H. Material Characteristics and Applications of Transparent Amorphous Oxide Semiconductors. NPG Asia Mater. 2010, 2 (1), 15–22. Mizoguchi, H.; Kamiya, T.; Matsuishi, S.; Hosono, H. A Germanate Transparent Conductive Oxide. Nat. Commun. 2011, 2, 470. When orbital hybridization between cation and anion is forbidden, a non-bonding state is formed. However, orbitals in cations can hybridize each other and the same is true for those of anions. The resultant energy level of cation-cation bonding state is lower than that of non-bonding state of cation orbital, while the energy level of anion-anion antibonding states is higher than that of non-bonding state of anion orbital. Thus, the ECBM and EVBM are mainly composed of the cation-cation bonding and anion-anion antibonding states, respectively. Please see the description in Supporting Information. Eng, H. W.; Barnes, P. W.; Auer, B. M.; Woodward, P. M. Investigations of the Electronic Structure of D0 Transition Metal Oxides Belonging to the Perovskite Family. J. Solid State Chem. 2003, 175 (1), 94–109.



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Doping Induced Polymorph and Carrier Polarity Changes in LaSeF

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