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Register a new userPrediction of new Group IV-V-VI monolayer semiconductors based on first principle calculation
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Two-dimension (2D) semiconductor materials have attracted much attention and research interest for their novel properties suitable for electronic and optoelectronic applications. In this paper, we have proposed an idea in new 2D materials design by using adjacent group elements to substitute half of the atoms in the primitive configurations to form isoelectronic compounds. We have successfully taken this idea on group V monolayers and have obtained many unexplored Group IV-V-VI monolayer compounds: P2SiS, As2SiS, As2GeSe, Sb2GeSe, Sb2SnTe, and Bi2SnTe. Relative formation energy calculations, phonon spectrum calculations, as well as finite-temperature molecular dynamics simulations confirm their stability and DFT calculations indicate that they are all semiconductors. This idea broadens the scope of group V semiconductors and we believe it can be extended to other type of 2D materials to obtain new semiconductors with better properties for optoelectronic and electronic applications.
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Heteroepitaxial growth of selected group IV-VI nitrides on various orientations of sapphire (alpha-Al2O3) is demonstrated using atomic layer deposition. High quality, epitaxial films are produced at significantly lower temperatures than required by conventional deposition methods. Characterization of electrical and superconducting properties of epitaxial films reveals a reduced room temperature resistivity and increased residual resistance ratio (RRR) for films deposited on sapphire compared to polycrystalline samples deposited concurrently on fused quartz substrates.
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Here, we clarify the central role of the miscut during group III-V/ group IV crystal growth. We show that the miscut first impacts the initial antiphase domain distribution, with two distinct nucleation-driven and terraces-driven regimes. It is then inferred how the antiphase domain distribution mean phase and mean lateral length are affected by the miscut. An experimental confirmation is given through the comparison of antiphase domain distributions in GaP and GaSb/AlSb samples grown on nominal and vicinal Si substrates. The antiphase domain burying step of GaP/Si samples is then observed at the atomic scale by scanning tunneling microscopy. The steps arising from the miscut allow growth rate imbalance between the two phases of the crystal and the growth conditions can deeply modify the imbalance coefficient, as illustrated with GaAs/Si. We finally explain how a monodomain III-V semiconductor configuration can be achieved even on low miscut substrates.
We perform systematic investigation on the geometric, energetic and electronic properties of group IV-VI binary monolayers (XY), which are the counterparts of phosphorene, by employing density functional theory based electronic structure calculations. For this purpose, we choose the binary systems XY consisting of equal numbers of group IV (X = C, Si, Ge, Sn) and group VI elements (Y = O, S, Se, Te) in three geometrical configurations, the puckered, buckled and planar structures. The results of binding energy calculations show that all the binary systems studied are energetically stable. It is observed that, the puckered structure, similar to that of phosphorene, is the energetically most stable geometric configuration. Our results of electronic band structure predict that puckered SiO and CSe are direct band semiconductors with gaps of 1.449 and 0.905 eV, respectively. Band structure of CSe closely resembles that of phosphorene. Remaining group IV-VI binary monolayers in the puckered configuration and all the buckled monolayers are also semiconductors, but with indirect band gaps. Importantly, we find that the difference between indirect and direct band gaps is very small for many puckered monolayers. Thus, there is a possibility of making these systems undergo transition from indirect to direct band gap semiconducting state by a suitable external influence. Indeed, we show in the present work that seven binary monolayers namely SnS, SiSe, GeSe, SnSe, SiTe, GeTe and SnTe become direct band gap semiconductors when they are subjected to a small mechanical strain (<= 3 %). This makes nine out of sixteen binary monolayers studied in the present work direct band gap semiconductors. Thus, there is a possibility of utilizing these binary counterparts of phosphorene in future light-emitting diodes and solar cells.
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