@article{kim_carrier_2019,
	title = {Carrier multiplication in van der {Waals} layered transition metal dichalcogenides},
	volume = {10},
	copyright = {2019 The Author(s)},
	issn = {2041-1723},
	url = {https://www.nature.com/articles/s41467-019-13325-9},
	doi = {10.1038/s41467-019-13325-9},
	abstract = {During carrier multiplication, high-energy free carriers in a given material relax by generation of additional electron-hole pairs. Here, the authors report evidence of carrier multiplication in multilayer MoTe2 and WSe2 films with up to 99\% conversation efficiency.},
	language = {en},
	number = {1},
	urldate = {2020-06-28},
	journal = {Nature Communications},
	author = {Kim, Ji-Hee and Bergren, Matthew R. and Park, Jin Cheol and Adhikari, Subash and Lorke, Michael and Frauenheim, Thomas and Choe, Duk-Hyun and Kim, Beom and Choi, Hyunyong and Gregorkiewicz, Tom and Lee, Young Hee},
	month = dec,
	year = {2019},
	pages = {1--9},
}

During carrier multiplication, high-energy free carriers in a given material relax by generation of additional electron-hole pairs. Here, the authors report evidence of carrier multiplication in multilayer MoTe2 and WSe2 films with up to 99% conversation efficiency.

@article{si_photoinduced_2019,
	title = {Photoinduced {Vacancy} {Ordering} and {Phase} {Transition} in {MoTe2}},
	volume = {19},
	issn = {1530-6984},
	url = {https://doi.org/10.1021/acs.nanolett.9b00613},
	doi = {10.1021/acs.nanolett.9b00613},
	abstract = {We show that non-equilibrium dynamics plays a central role in the photoinduced 2H-to-1T′ phase transition of MoTe2. The phase transition is initiated by a local ordering of Te vacancies, followed by a 1T′ structural change in the original 2H lattice. The local 1T′ region serves as a seed to gather more vacancies into ordering and subsequently induces a further growth of the 1T′ phase. Remarkably, this process is controlled by photogenerated excited carriers as they enhance vacancy diffusion, increase the speed of vacancy ordering, and are hence vital to the 1T′ phase transition. This mechanism can be contrasted to the current model requiring a collective sliding of a whole Te atomic layer, which is thermodynamically highly unlikely. By uncovering the key roles of photoexcitations, our results may have important implications for finely controlling phase transitions in transition metal dichalcogenides.},
	number = {6},
	urldate = {2020-06-28},
	journal = {Nano Letters},
	author = {Si, Chen and Choe, Dukhyun and Xie, Weiyu and Wang, Han and Sun, Zhimei and Bang, Junhyeok and Zhang, Shengbai},
	month = jun,
	year = {2019},
	pages = {3612--3617},
}

We show that non-equilibrium dynamics plays a central role in the photoinduced 2H-to-1T′ phase transition of MoTe2. The phase transition is initiated by a local ordering of Te vacancies, followed by a 1T′ structural change in the original 2H lattice. The local 1T′ region serves as a seed to gather more vacancies into ordering and subsequently induces a further growth of the 1T′ phase. Remarkably, this process is controlled by photogenerated excited carriers as they enhance vacancy diffusion, increase the speed of vacancy ordering, and are hence vital to the 1T′ phase transition. This mechanism can be contrasted to the current model requiring a collective sliding of a whole Te atomic layer, which is thermodynamically highly unlikely. By uncovering the key roles of photoexcitations, our results may have important implications for finely controlling phase transitions in transition metal dichalcogenides.

@article{agiorgousis_machine_2019,
	title = {Machine {Learning} {Augmented} {Discovery} of {Chalcogenide} {Double} {Perovskites} for {Photovoltaics}},
	volume = {2},
	issn = {2513-0390},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adts.201800173},
	doi = {10.1002/adts.201800173},
	abstract = {Hybrid organic inorganic perovskite solar cells based on CH3NH3PbI3 have drastically increased in efficiency over the past several years and are competitive with decades-old photovoltaic materials such as CdTe. Despite this impressive increase, significant issues still remain due to the intrinsic instability of CH3NH3PbI3 which degrades into carcinogenic PbI2. Recently, double halide perovskites which use a pair of 1+–3+ cations to replace Pb2+, such as Cs2InSbI6, and chalcogenide perovskites, such as BaZrS3, have been explored as potential replacements. In this work, double chalcogenide perovskites are explored to identify novel photovoltaic absorbers that can replace CH3NH3PbI3. Due to the large space of possible compounds, machine learning methods are used to classify materials as potential photovoltaic absorbers using data from the periodic table, eliminating wasteful computation. A random forest algorithm achieves a cross-validation accuracy of 86.4\% on the constructed data set. Over 450 possible replacements are identified via traditional and statistical methods with Ba2AlNbS6, Ba2GaNbS6, Ca2GaNbS6, Sr2InNbS6, and Ba2SnHfS6 as the most promising alternative when thermodynamic stability, kinetic stability, and optical absorption are considered.},
	language = {en},
	number = {5},
	urldate = {2020-06-28},
	journal = {Advanced Theory and Simulations},
	author = {Agiorgousis, Michael L. and Sun, Yi-Yang and Choe, Duk-Hyun and West, Damien and Zhang, Shengbai},
	year = {2019},
	keywords = {density functional theory, machine learning, perovskites, photovoltaics},
	pages = {1800173},
}

Hybrid organic inorganic perovskite solar cells based on CH3NH3PbI3 have drastically increased in efficiency over the past several years and are competitive with decades-old photovoltaic materials such as CdTe. Despite this impressive increase, significant issues still remain due to the intrinsic instability of CH3NH3PbI3 which degrades into carcinogenic PbI2. Recently, double halide perovskites which use a pair of 1+–3+ cations to replace Pb2+, such as Cs2InSbI6, and chalcogenide perovskites, such as BaZrS3, have been explored as potential replacements. In this work, double chalcogenide perovskites are explored to identify novel photovoltaic absorbers that can replace CH3NH3PbI3. Due to the large space of possible compounds, machine learning methods are used to classify materials as potential photovoltaic absorbers using data from the periodic table, eliminating wasteful computation. A random forest algorithm achieves a cross-validation accuracy of 86.4% on the constructed data set. Over 450 possible replacements are identified via traditional and statistical methods with Ba2AlNbS6, Ba2GaNbS6, Ca2GaNbS6, Sr2InNbS6, and Ba2SnHfS6 as the most promising alternative when thermodynamic stability, kinetic stability, and optical absorption are considered.

@article{choe_band_2018,
	title = {Band {Alignment} and the {Built}-in {Potential} of {Solids}},
	volume = {121},
	url = {https://link.aps.org/doi/10.1103/PhysRevLett.121.196802},
	doi = {10.1103/PhysRevLett.121.196802},
	abstract = {The built-in potential is of central importance to the understanding of many interfacial phenomena because it determines the band alignment at the interface. Despite its importance, its exact sign and magnitude have generally been recognized as ill-defined quantities for more than half a century. Here, we provide a common energy reference of bulk matter which leads to an unambiguous definition of the built-in potential and innate (i.e., bulk) band alignment. Further, we find that the built-in potential is explicitly determined by the bulk properties of the constituent materials when the system is in electronic equilibrium, while the interface plays a role only in the absence of equilibrium. Our quantitative theory enables a unified description of a variety of important properties of interfaces, ranging from work functions to Schottky barriers in electronic devices.},
	number = {19},
	urldate = {2020-06-28},
	journal = {Physical Review Letters},
	author = {Choe, Duk-Hyun and West, Damien and Zhang, Shengbai},
	month = nov,
	year = {2018},
	pages = {196802},
}

The built-in potential is of central importance to the understanding of many interfacial phenomena because it determines the band alignment at the interface. Despite its importance, its exact sign and magnitude have generally been recognized as ill-defined quantities for more than half a century. Here, we provide a common energy reference of bulk matter which leads to an unambiguous definition of the built-in potential and innate (i.e., bulk) band alignment. Further, we find that the built-in potential is explicitly determined by the bulk properties of the constituent materials when the system is in electronic equilibrium, while the interface plays a role only in the absence of equilibrium. Our quantitative theory enables a unified description of a variety of important properties of interfaces, ranging from work functions to Schottky barriers in electronic devices.

@article{zhang_quantum_2018,
	title = {Quantum oscillation in carrier transport in two-dimensional junctions},
	volume = {10},
	issn = {2040-3372},
	url = {https://pubs.rsc.org/en/content/articlelanding/2018/nr/c8nr01359d},
	doi = {10.1039/C8NR01359D},
	abstract = {Two-dimensional (2D) junction devices have recently attracted considerable attention. Here, we show that most 2D junction structures, whether vertical or lateral, act as a lateral monolayer–bilayer–monolayer junction in their operation. In particular, a vertical structure cannot function as a vertical junction as having been widely believed in the literature. Due to a larger electrostatic screening, the bilayer region in the junction always has a smaller bandgap than its monolayer counterpart. As a result, a potential well, aside from the usual potential barrier, will form universally in the bilayer region to affect the hole or electron quantum transport in the form of transmission or reflection. Taking black phosphorus as an example, our calculations using a non-equilibrium Green function combined with density functional theory show a distinct oscillation in the transmission coefficient in a two-electrode prototypical device, and the results can be qualitatively understood using a simple quantum well model.},
	language = {en},
	number = {17},
	urldate = {2020-06-28},
	journal = {Nanoscale},
	author = {Zhang, Junfeng and Xie, Weiyu and Agiorgousis, Michael L. and Choe, Duk-Hyun and Meunier, Vincent and Xu, Xiaohong and Zhao, Jijun and Zhang, Shengbai},
	month = may,
	year = {2018},
	pages = {7912--7917},
}

Two-dimensional (2D) junction devices have recently attracted considerable attention. Here, we show that most 2D junction structures, whether vertical or lateral, act as a lateral monolayer–bilayer–monolayer junction in their operation. In particular, a vertical structure cannot function as a vertical junction as having been widely believed in the literature. Due to a larger electrostatic screening, the bilayer region in the junction always has a smaller bandgap than its monolayer counterpart. As a result, a potential well, aside from the usual potential barrier, will form universally in the bilayer region to affect the hole or electron quantum transport in the form of transmission or reflection. Taking black phosphorus as an example, our calculations using a non-equilibrium Green function combined with density functional theory show a distinct oscillation in the transmission coefficient in a two-electrode prototypical device, and the results can be qualitatively understood using a simple quantum well model.

@article{lucking_traditional_2018,
	title = {Traditional {Semiconductors} in the {Two}-{Dimensional} {Limit}},
	volume = {120},
	url = {https://link.aps.org/doi/10.1103/PhysRevLett.120.086101},
	doi = {10.1103/PhysRevLett.120.086101},
	abstract = {Interest in two-dimensional materials has exploded in recent years. Not only are they studied due to their novel electronic properties, such as the emergent Dirac fermion in graphene, but also as a new paradigm in which stacking layers of distinct two-dimensional materials may enable different functionality or devices. Here, through first-principles theory, we reveal a large new class of two-dimensional materials which are derived from traditional III-V, II-VI, and I-VII semiconductors. It is found that in the ultrathin limit the great majority of traditional binary semiconductors studied (a series of 28 semiconductors) are not only kinetically stable in a two-dimensional double layer honeycomb structure, but more energetically stable than the truncated wurtzite or zinc-blende structures associated with three dimensional bulk. These findings both greatly increase the landscape of two-dimensional materials and also demonstrate that in the double layer honeycomb form, even ordinary semiconductors, such as GaAs, can exhibit exotic topological properties.},
	number = {8},
	urldate = {2020-06-28},
	journal = {Physical Review Letters},
	author = {Lucking, Michael C. and Xie, Weiyu and Choe, Duk-Hyun and West, Damien and Lu, Toh-Ming and Zhang, S. B.},
	month = feb,
	year = {2018},
	pages = {086101},
}

Interest in two-dimensional materials has exploded in recent years. Not only are they studied due to their novel electronic properties, such as the emergent Dirac fermion in graphene, but also as a new paradigm in which stacking layers of distinct two-dimensional materials may enable different functionality or devices. Here, through first-principles theory, we reveal a large new class of two-dimensional materials which are derived from traditional III-V, II-VI, and I-VII semiconductors. It is found that in the ultrathin limit the great majority of traditional binary semiconductors studied (a series of 28 semiconductors) are not only kinetically stable in a two-dimensional double layer honeycomb structure, but more energetically stable than the truncated wurtzite or zinc-blende structures associated with three dimensional bulk. These findings both greatly increase the landscape of two-dimensional materials and also demonstrate that in the double layer honeycomb form, even ordinary semiconductors, such as GaAs, can exhibit exotic topological properties.

@article{han_three-dimensional_2017,
	title = {Three-dimensional buckled honeycomb boron lattice with vacancies as an intermediate phase on the transition pathway from α-{B} to γ-{B}},
	volume = {9},
	issn = {1884-4049, 1884-4057},
	url = {http://www.nature.com/articles/am201798},
	doi = {10.1038/am.2017.98},
	language = {en},
	number = {7},
	urldate = {2020-06-28},
	journal = {NPG Asia Materials},
	author = {Han, Woo Hyun and Oh, Young Jun and Choe, Duk-Hyun and Kim, Sunghyun and Lee, In-Ho and Chang, Kee Joo},
	month = jul,
	year = {2017},
	pages = {e400--e400},
}

@article{cho_te_2017,
	title = {Te vacancy-driven superconductivity in orthorhombic molybdenum ditelluride},
	volume = {4},
	issn = {2053-1583},
	url = {https://iopscience.iop.org/article/10.1088/2053-1583/aa735e},
	doi = {10.1088/2053-1583/aa735e},
	number = {2},
	urldate = {2020-06-28},
	journal = {2D Materials},
	author = {Cho, Suyeon and Kang, Se Hwang and Yu, Ho Sung and Kim, Hyo Won and Ko, Wonhee and Hwang, Sung Woo and Han, Woo Hyun and Choe, Duk-Hyun and Jung, Young Hwa and Chang, Kee Joo and Lee, Young Hee and Yang, Heejun and Kim, Sung Wng},
	month = jun,
	year = {2017},
	pages = {021030},
}

@article{kim_long-range_2017,
	title = {Long-{Range} {Lattice} {Engineering} of {MoTe2} by a {2D} {Electride}},
	volume = {17},
	issn = {1530-6984},
	url = {https://doi.org/10.1021/acs.nanolett.6b05199},
	doi = {10.1021/acs.nanolett.6b05199},
	abstract = {Doping two-dimensional (2D) semiconductors beyond their degenerate levels provides the opportunity to investigate extreme carrier density-driven superconductivity and phase transition in 2D systems. Chemical functionalization and the ionic gating have achieved the high doping density, but their effective ranges have been limited to ∼1 nm, which restricts the use of highly doped 2D semiconductors. Here, we report on electron diffusion from the 2D electride [Ca2N]+·e– to MoTe2 over a distance of 100 nm from the contact interface, generating an electron doping density higher than 1.6 × 1014 cm–2 and a lattice symmetry change of MoTe2 as a consequence of the extreme doping. The long-range lattice symmetry change, suggesting a length scale surpassing the depletion width of conventional metal–semiconductor junctions, was a consequence of the low work function (2.6 eV) with highly mobile anionic electron layers of [Ca2N]+·e–. The combination of 2D electrides and layered materials yields a novel material design in terms of doping and lattice engineering.},
	number = {6},
	urldate = {2020-06-28},
	journal = {Nano Letters},
	author = {Kim, Sera and Song, Seunghyun and Park, Jongho and Yu, Ho Sung and Cho, Suyeon and Kim, Dohyun and Baik, Jaeyoon and Choe, Duk-Hyun and Chang, K. J. and Lee, Young Hee and Kim, Sung Wng and Yang, Heejun},
	month = jun,
	year = {2017},
	pages = {3363--3368},
}

Doping two-dimensional (2D) semiconductors beyond their degenerate levels provides the opportunity to investigate extreme carrier density-driven superconductivity and phase transition in 2D systems. Chemical functionalization and the ionic gating have achieved the high doping density, but their effective ranges have been limited to ∼1 nm, which restricts the use of highly doped 2D semiconductors. Here, we report on electron diffusion from the 2D electride [Ca2N]+·e– to MoTe2 over a distance of 100 nm from the contact interface, generating an electron doping density higher than 1.6 × 1014 cm–2 and a lattice symmetry change of MoTe2 as a consequence of the extreme doping. The long-range lattice symmetry change, suggesting a length scale surpassing the depletion width of conventional metal–semiconductor junctions, was a consequence of the low work function (2.6 eV) with highly mobile anionic electron layers of [Ca2N]+·e–. The combination of 2D electrides and layered materials yields a novel material design in terms of doping and lattice engineering.

@article{sung_tuning_2016,
	title = {Tuning {Dirac} points by strain in {MoX2} nanoribbons ({X} = {S}, {Se}, {Te}) with a {1T}′ structure},
	volume = {18},
	issn = {1463-9084},
	url = {https://pubs.rsc.org/en/content/articlelanding/2016/cp/c6cp02204a},
	doi = {10.1039/C6CP02204A},
	abstract = {For practical applications of two-dimensional topological insulators, large band gaps and Dirac states within the band gap are desirable because they allow for device operation at room temperature and quantum transport without dissipation. Based on first-principles density functional calculations, we report the tunability of the electronic structure by strain engineering in quasi-one-dimensional nanoribbons of transition metal dichalcogenides with a 1T′ structure, MoX2 with X = (S, Se, Te). We find that both the band gaps and Dirac points in 1T′-MoX2 can be engineered by applying an external strain, thereby leading to a single Dirac cone within the bulk band gap. Considering the gap size and the location of the Dirac point, we suggest that, among 1T′-MoX2 nanoribbons, MoSe2 is the most suitable candidate for quantum spin Hall (QSH) devices.},
	language = {en},
	number = {24},
	urldate = {2020-06-28},
	journal = {Physical Chemistry Chemical Physics},
	author = {Sung, Ha-Jun and Choe, Duk-Hyun and Chang, K. J.},
	month = jun,
	year = {2016},
	pages = {16361--16366},
}

For practical applications of two-dimensional topological insulators, large band gaps and Dirac states within the band gap are desirable because they allow for device operation at room temperature and quantum transport without dissipation. Based on first-principles density functional calculations, we report the tunability of the electronic structure by strain engineering in quasi-one-dimensional nanoribbons of transition metal dichalcogenides with a 1T′ structure, MoX2 with X = (S, Se, Te). We find that both the band gaps and Dirac points in 1T′-MoX2 can be engineered by applying an external strain, thereby leading to a single Dirac cone within the bulk band gap. Considering the gap size and the location of the Dirac point, we suggest that, among 1T′-MoX2 nanoribbons, MoSe2 is the most suitable candidate for quantum spin Hall (QSH) devices.

@article{choe_understanding_2016,
	title = {Understanding topological phase transition in monolayer transition metal dichalcogenides},
	volume = {93},
	url = {https://link.aps.org/doi/10.1103/PhysRevB.93.125109},
	doi = {10.1103/PhysRevB.93.125109},
	abstract = {Despite considerable interest in layered transition metal dichalcogenides (TMDs), such as MX2 with M=(Mo,W) and X=(S,Se,Te), the physical origin of their topological nature is still poorly understood. In the conventional view of topological phase transition (TPT), the nontrivial topology of electron bands in TMDs is caused by the band inversion between metal d- and chalcogen p-orbital bands where the former is pulled down below the latter. Here, we show that, in TMDs, the TPT is entirely different from the conventional speculation. In particular, MS2 and MSe2 exhibits the opposite behavior of TPT such that the chalcogen p-orbital band moves down below the metal d-orbital band. More interestingly, in MTe2, the band inversion occurs between the metal d-orbital bands. Our findings cast doubts on the common view of TPT and provide clear guidelines for understanding the topological nature in new topological materials to be discovered.},
	number = {12},
	urldate = {2020-06-28},
	journal = {Physical Review B},
	author = {Choe, Duk-Hyun and Sung, Ha-Jun and Chang, K. J.},
	month = mar,
	year = {2016},
	pages = {125109},
}

Despite considerable interest in layered transition metal dichalcogenides (TMDs), such as MX2 with M=(Mo,W) and X=(S,Se,Te), the physical origin of their topological nature is still poorly understood. In the conventional view of topological phase transition (TPT), the nontrivial topology of electron bands in TMDs is caused by the band inversion between metal d- and chalcogen p-orbital bands where the former is pulled down below the latter. Here, we show that, in TMDs, the TPT is entirely different from the conventional speculation. In particular, MS2 and MSe2 exhibits the opposite behavior of TPT such that the chalcogen p-orbital band moves down below the metal d-orbital band. More interestingly, in MTe2, the band inversion occurs between the metal d-orbital bands. Our findings cast doubts on the common view of TPT and provide clear guidelines for understanding the topological nature in new topological materials to be discovered.

@article{choe_universal_2015,
	title = {Universal {Conductance} {Fluctuation} in {Two}-{Dimensional} {Topological} {Insulators}},
	volume = {5},
	issn = {2045-2322},
	url = {http://www.nature.com/articles/srep10997},
	doi = {10.1038/srep10997},
	language = {en},
	number = {1},
	urldate = {2020-06-28},
	journal = {Scientific Reports},
	author = {Choe, Duk-Hyun and Chang, K. J.},
	month = sep,
	year = {2015},
	pages = {10997},
}

@article{cho_phase_2015,
	title = {Phase patterning for ohmic homojunction contact in {MoTe2}},
	volume = {349},
	issn = {0036-8075, 1095-9203},
	url = {https://www.sciencemag.org/lookup/doi/10.1126/science.aab3175},
	doi = {10.1126/science.aab3175},
	language = {en},
	number = {6248},
	urldate = {2020-06-28},
	journal = {Science},
	author = {Cho, S. and Kim, S. and Kim, J. H. and Zhao, J. and Seok, J. and Keum, D. H. and Baik, J. and Choe, D.-H. and Chang, K. J. and Suenaga, K. and Kim, S. W. and Lee, Y. H. and Yang, H.},
	month = aug,
	year = {2015},
	pages = {625--628},
}

@article{keum_bandgap_2015,
	title = {Bandgap opening in few-layered monoclinic {MoTe} 2},
	volume = {11},
	copyright = {2014 Nature Publishing Group},
	issn = {1745-2481},
	url = {https://www.nature.com/articles/nphys3314},
	doi = {10.1038/nphys3314},
	abstract = {Monoclinic transition metal dichalcogenides offer the possibility of topological quantum devices, but they are difficult to realize. One route may be through switching from the common hexagonal phase, for which a method is now shown.},
	language = {en},
	number = {6},
	urldate = {2020-06-28},
	journal = {Nature Physics},
	author = {Keum, Dong Hoon and Cho, Suyeon and Kim, Jung Ho and Choe, Duk-Hyun and Sung, Ha-Jun and Kan, Min and Kang, Haeyong and Hwang, Jae-Yeol and Kim, Sung Wng and Yang, Heejun and Chang, K. J. and Lee, Young Hee},
	month = jun,
	year = {2015},
	pages = {482--486},
}

Monoclinic transition metal dichalcogenides offer the possibility of topological quantum devices, but they are difficult to realize. One route may be through switching from the common hexagonal phase, for which a method is now shown.

@article{song_bandgap_2015,
	title = {Bandgap {Widening} of {Phase} {Quilted}, {2D} {MoS2} by {Oxidative} {Intercalation}},
	volume = {27},
	issn = {1521-4095},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.201500649},
	doi = {10.1002/adma.201500649},
	abstract = {Controllable bandgap widening from 1.8 to 2.6 eV is reported from oxidized MoS2 sheets that are composed of quilted phases of various MoSxOy flakes. The exfoliated flakes have large size (≥100 μm × 100 μm) sheets with average thickness of 1.7 nm. Remarkably, fine reversible tuning of the bandgap is achieved by postprocessing sulfurization of the MoSxOy sheets.},
	number = {20},
	urldate = {2020-06-28},
	journal = {Advanced Materials},
	author = {Song, Sung Ho and Kim, Bo Hyun and Choe, Duk-Hyun and Kim, Jin and Kim, Dae Chul and Lee, Dong Ju and Kim, Jung Mo and Chang, Kee Joo and Jeon, Seokwoo},
	year = {2015},
	keywords = {2D transition metal dichalcogenides, bandgap widening, intercalation compounds, molybdenum disulfide, photoluminescence},
	pages = {3152--3158},
}

Controllable bandgap widening from 1.8 to 2.6 eV is reported from oxidized MoS2 sheets that are composed of quilted phases of various MoSxOy flakes. The exfoliated flakes have large size (≥100 μm × 100 μm) sheets with average thickness of 1.7 nm. Remarkably, fine reversible tuning of the bandgap is achieved by postprocessing sulfurization of the MoSxOy sheets.

@article{sung_effects_2014,
	title = {The effects of surface polarity and dangling bonds on the electronic properties of monolayer and bilayer {MoS} $_{\textrm{2}}$ on \textit{α} -quartz},
	volume = {16},
	issn = {1367-2630},
	url = {https://iopscience.iop.org/article/10.1088/1367-2630/16/11/113055},
	doi = {10.1088/1367-2630/16/11/113055},
	number = {11},
	urldate = {2020-06-28},
	journal = {New Journal of Physics},
	author = {Sung, Ha-Jun and Choe, Duk-Hyun and Chang, K J},
	month = nov,
	year = {2014},
	pages = {113055},
}

@article{choe_effect_2012,
	title = {Effect of {Dimensionality} on the {Localization} {Behavior} in {Hydrogenated} {Graphene} {Systems}},
	volume = {12},
	issn = {1530-6984},
	url = {https://doi.org/10.1021/nl302207p},
	doi = {10.1021/nl302207p},
	abstract = {Recently, several experiments have shown that graphene exhibits a metal-to-insulator transition by hydrogenation. Here we theoretically study the transport properties of hydrogenated graphene and graphene nanoribbons (GNRs), focusing on the conductance fluctuation behavior in the localized regime. Using a simple model for the conductance distribution in the quasi-localized regime where the conventional theory fails, we derive the modified single parameter scaling (SPS) relations for quasi-one-dimensional (Q1D) GNRs as well as two-dimensional (2D) graphene. We show that, as the dimensional crossover occurs from 2D to Q1D, the shape of the conductance distribution evolves from a positively skewed distribution to a log-normal distribution. We predict that GNRs with widths much larger than the localization lengths do not behave as a Q1D system. Our results provide fundamental insights into the dimensionality change not only in graphene, but also in general mesoscopic systems in the localized regime.},
	number = {10},
	urldate = {2020-06-28},
	journal = {Nano Letters},
	author = {Choe, Duk-Hyun and Chang, K. J.},
	month = oct,
	year = {2012},
	pages = {5175--5180},
}

Recently, several experiments have shown that graphene exhibits a metal-to-insulator transition by hydrogenation. Here we theoretically study the transport properties of hydrogenated graphene and graphene nanoribbons (GNRs), focusing on the conductance fluctuation behavior in the localized regime. Using a simple model for the conductance distribution in the quasi-localized regime where the conventional theory fails, we derive the modified single parameter scaling (SPS) relations for quasi-one-dimensional (Q1D) GNRs as well as two-dimensional (2D) graphene. We show that, as the dimensional crossover occurs from 2D to Q1D, the shape of the conductance distribution evolves from a positively skewed distribution to a log-normal distribution. We predict that GNRs with widths much larger than the localization lengths do not behave as a Q1D system. Our results provide fundamental insights into the dimensionality change not only in graphene, but also in general mesoscopic systems in the localized regime.

@article{choe_electronic_2010,
	title = {Electronic structure and transport properties of hydrogenated graphene and graphene nanoribbons},
	volume = {12},
	issn = {1367-2630},
	url = {https://iopscience.iop.org/article/10.1088/1367-2630/12/12/125005},
	doi = {10.1088/1367-2630/12/12/125005},
	number = {12},
	urldate = {2020-06-28},
	journal = {New Journal of Physics},
	author = {Choe, D H and Bang, Junhyeok and Chang, K J},
	month = dec,
	year = {2010},
	pages = {125005},
}