Correction to "Accurate Assessments of the Electronic Structures of Ultrathin PtSe2: Bandgap Quantification and Critical Thickness for the Metal-Semiconductor Transition".

Pressure-Induced Intermetallic Charge Transfer and Semiconductor-Metal Transition in Two-Dimensional AgRuO ₃

Semiconductor–metal and metal–semiconductor transitions in twisting graphene nanoribbons

Crystal phase transitions can form a new type of heterojunctionwith different atomic arrangements in the same material: crystal phaseheterojunction (CPHJ). The CPHJ has an inherently strong impact onband engineering without concerns over critical thicknesses with misfitdislocations and a semiconductor–metal transition. In-planeCPHJ was recently demonstrated in two-dimensional (2D) transition-metaldichalcogenide (TMD) materials and utilized for conventional planarfield-effect transistor applications. However, scalability such asgate electrostatic control, miniaturization, and multigate structurehave been limited because of the geometrical issue. Here, we demonstrateda transistor using the CPHJ with a vertical gate-all-around structureby forming a CPHJ in conventional III–V semiconductors. TheCPHJ, composed of wurtzite InP nanowires with zincblende InP substrates,showed an atomically flat heterojunction without dislocations andindicated a Type-II band discontinuity across the junction. The CPHJtransistor had moderate to good gate electrostatic controllabilitywith high on-state currents and transconductance. The CPHJ offer willprovide a new switching mechanism and add a new junction and devicedesign choice to the long history of transistors.

The intrinsic critical ferroelectric thickness of epitaxial ultrathin capacitors of incipient ferroelectric $\mathrm{BaZr}{\mathrm{O}}_{3}$ (BZO) films with realistic $\mathrm{SrRu}{\mathrm{O}}_{3}$ (SRO) electrodes is investigated by first-principles calculations based on density functional theory. We reveal that polarization can stably exist even in one-unit-cell thick BZO films, i.e., absence of critical thickness, whereas the widely investigated proper ferroelectrics like $\mathrm{BaTi}{\mathrm{O}}_{3}$ and $\mathrm{SrTi}{\mathrm{O}}_{3}$ films have no polarization. The influences of realistic ferroelectric-electrode interface and misfit strain on the ionic and electronic structures of the BZO-SRO thin film system have been examined under the short-circuited boundary condition. It is found that the ionic polarization of conductive SRO electrodes can effectively strengthen the screening of bound charges at the interface, which greatly reduces the depolarization field in the BZO films. Furthermore, the epitaxial misfit strain remarkably enhances the polarization through the enhancement of hybridization of $\mathrm{Zr}$ and $\mathrm{O}$ electron orbitals, resulting in the disappearance of ferroelectric critical thickness. Our findings are beyond the critical thickness of proper ferroelectrics and are thus promising for future nanometer-scale ferroelectric device such as high-density ferroelectric memory.

Semiconductor-metal transition induced by giant Stark effect in blue phosphorene nanoribbons

The electronic structures, Rashba spin-orbit couplings, and transport properties of InSb nanowires and nanofilms are investigated theoretically. When both the radius of the wire (or the thickness of the film) and the electric field are large, the electron bands and hole bands overlap, and the Fermi level crosses with some bands, which means that the semiconductors transit into metals. Meanwhile, the Rashba coefficients behave in an abnormal way. The conductivities increase dramatically when the electric field is larger than a critical value. This semiconductor-metal transition is observable at the room temperature.

By performing first-principles electronic structure and transport calculations, we have demonstrated the electronic structure and transport properties of single layer zigzag graphene nanoribbons with armchair edges and the effect of edge-vacancy defects. It is shown that perfect zigzag graphene nanoribbons are semiconductor with certain energy gaps which will become smaller due to the edge-vacancy defects combining with semiconductor-metal transition. This result may contribute to the electronic structure sewing of the graphene nanoribbons in the energy-band engineering.

The electronic energy-band structure of the PrBaCo2O5 + δ cobaltite at the oxygen content close to 5.5 are calculated by the first-principle PAW methods. The semiconductor–metal phase transition at 5 + δ = 5.5 is shown to be a result of the transition of cobalt atoms in the octahedral environment from the high-spin to low-spin state. The cause of the appearance of the metallic conduction is an increase in the energy of antibonding eg states of pyramidal cobalt atoms, and, as a result, they are at the Fermi level, thereby determining the metallic character of the system. The effect of a deviation of the oxygen content from 5.5 on the energy-band structure and the conductivity is studied. The semiconductor–metal transition is shown can be observed only in a narrow range of the values of 5 + δ lower 5.5.

LiOHFeSe is a layered material that has been extensively investigated for its magnetic states and superconductivity. In this work, an isomer of LiOHFeSe containing FeO and LiSeH layers is computationally investigated. The electron correlation, electronic structures, magnetism and optical properties are calculated and analyzed for both bulk and ultrathin heterostructures. The bulk LiSeHFeO has antiferromagnetic (AFM) state as ground state with a band gap of 1.38 eV. When the system turns from AFM to FM and to paramagnetic states, the band gap shows a monotonic decrease to metallic. On the other hand, LiSeHFeO shows different absorption spectra at different magnetic states, especially in long wavelength region. Then, two types of sandwich heterostructures with two LiSeH and one FeO layer or in a reversal are investigated on electronic structures and optical absorptions. Moreover, their behaviors with the presence of electric field are explored, where a semiconductor–metal transition is observed for the heterostructure of two FeO layers and one LiSeH layer with the increased electric field. These findings may draw attentions to these materials so as to promote the experimental synthesis and potential applications of LiSeHFeO in bulk or film.

“1/f” noise in thin metal films interacting with silicon substrates

It still remains a challenge to prepare a room‐temperature responsive VO2‐based thermochromic film assembly that could balance high visible light transmittance (Tlum) and solar light modulation efficiency (ΔTsol). In the current research, Ta‐doped VO2 films, composed of large single‐crystalline domains, were prepared through magnetron sputtering and postvacuum annealing; their structural, electrical, and optical properties were deeply analyzed. The doped films showed distinct semiconductor‐to‐metal transition (SMT) behaviors, and it was seen that the resistance change across the SMT was still near 100 times when the SMT temperature (Tc) was decreased to ∼35°C. The analysis indicated that the Ta dopants formed shallow donors 0.1–0.14 eV below the conduction band for semiconductor phase. The n and k were obtained from the regressive analysis of the optical spectra, which were further used to obtained absorption coefficients and gap energies, based on which the electronic structure was discussed. Under the guidance of optical designs, a four‐layer SiO2/TiO2/Ta‐VO2/TiO2/substrate was fabricated; this obtained the average Tlum of ∼53% and the ΔTsol of ∼14%, while the Tc was reduced to ∼35°C. A remarkable balance between the high Tlum and high ΔTsol was achieved for the multilayer film assemblies, which can be increased by further tuned the layer thicknesses and VO2 structures.

The study of impurities and defects in semiconductors is of fundamental interest and is important for technological applications. This monograph is a first attempt to generalise experimental data and theoretical interpretation about the nature and behaviour of impurity atoms of transition metals in semiconductors. The nature of impurities and changes in their electronic structure are analysed. The molecualr orbital approach is followed extensively in the theoretical interpretation, with particular emphasis on crystal field splitting, electron paramagnetic resonance and optical absorption spectoscopies. Coverage of experimental data is extensive with more the 300 references to the literature. This is a translation of a Russian text published in 1983. The authors have updated the content for the English language edition. This book will be of interest to scientists and engineers in solid state physics and chemistry, materials science and electronic engineering. It should also be useful for postgraduate students in these fields.

Based on first-principles electronic structure and transport calculations, we have studied electronic structure and transport properties of graphene nanoribbons with single vacancy defects. It is shown that introduction of the single vacancy defects leads to a flat band belt at the Fermi energy level for graphene nanoribbons and the semiconductor-metal transition in zigzag semiconducting graphene nanoribbons, which is useful in the energy-band engineering. Armchair graphene nanoribbons with odd width are metallic with good electric conduction while armchair graphene nanoribbons with even width have metallic band structures with character of the group IV semiconductor. Single vacancy defects weakens the conduction of armchair graphene nanoribbons with odd width while obviously strengthens the conduction of armchair graphene nanoribbons with even width.

We mainly study the Zeeman effect on electronic structure of carbon nanotori in the presence of magnetic field (B) perpendicular to the tori's plane. As a function of magnetic flux (ϕ), the energy gap (Eg) and density of states (DOS) near the Fermi level are obtained in the case of with and without considering the Zeeman effect. Without spin-B interaction, the ϕ-dependent electronic structure would exhibit the periodical Aharonov–Bohm (AB) oscillation. A magnetic-field-induced semiconductor-metal transition is indicated in the variation of energy gap and DOS of armchair tori. The Zeeman effect on electronic structure is notable at relatively large ϕ (~100ϕ0, with ϕ0 = h/e), e.g., more phase transition points may appear in the Eg - B dependence for armchair tori, and the destruction of periodical AB oscillation is distinct due to the Zeeman effect. These results may be observed by scanning tunneling spectroscopy measurement.

The calculations of electronic band structure of the cobaltite PrBaCo2O5+d for the content of oxygen near 5.5 have been performed using the first-principle PAW method. It has been shown that the semiconductor-metal transition near 5+d=5.5 is associated with the conversion of cobalt atoms in octahedral oxygen surrounding from high to low spin state and the similar atoms in pyramidal surrounding from the low to high spin state. The metal conductivity appears due to raising of the energy of pyramidal Co eg antibonding states. As a result these states turn up at the Fermi level thus defining the conductivity. The effect of oxygen content deviation from 5.5 on the band structure and conductivity has been studies. It is shown that the semiconductor-metal transition can be observed in the narrow range of 5+d below 5.5.