Electrical and optical properties of hydrogen plasma treatedβ-Ga_(2)O_(3) thin films

The behavior of H inβ-Ga_(2)O_(3) is of substantial interest because it is a common residual impurity that is present inβ-Ga_(2)O_(3),regardless of the synthesis methods.Herein,we report the influences of H-plasma exposure on the electric and optical properties of the heteroepitaxialβ-Ga_(2)O_(3) thin films grown on sapphire substrates by chemical vapor deposition.The results in-dicate that the H incorporation leads to a significantly increased electrical conductivity,a greatly reduced defect-related photolu-minescence emission,and a slightly enhanced transmittance,while it has little effect on the crystalline quality of theβ-Ga_(2)O_(3) films.The significant changes in the electrical and optical properties ofβ-Ga_(2)O_(3) may originate from the formation of shallow donor states and the passivation of the defects by the incorporated H.Temperature dependent electrical properties of the H-in-corporatedβ-Ga_(2)O_(3) films are also investigated,and the dominant scattering mechanisms at various temperatures are dis-cussed.

A Research Summary on the Chemical Constituents and Pharmacological Effects of the National Medicine Polygonum capitatum

Polygonum capitatum Buch.Ham.ex D.Don is a commonly used medicine in Zhuang people’s settlements,which has antipyretic,wind and evil-dispelling,dehumidifying and analgesic effects.The research on the chemical composition of P.capitatum began in the 1980 s.Modern scientific research has shown that it has antibacterial,cooling and blood sugar lowering effect.In order to better develop and utilize P.capitatum,this paper reviewed the progress of the chemical composition and pharmacological research of P.capitatum.

Remote heteroepitaxy of transition metal dichalcogenides through monolayer hexagonal boron nitride

As a very promising epitaxy technology,the remote epitaxy has attracted extensive attention in recent years,in which graphene is the most used interlayer material.As an isomorphic of graphene,two-dimensional(2D)hexagonal boron nitride(h-BN),is another promising interlayer for the remote epitaxy.However,there is a current debate on the feasibility of using h-BN as interlayer in the remote epitaxy.Herein,we demonstrate that the potential field of sapphire can completely penetrate monolayer h-BN,and hence the remote epitaxy of ZrS_(2) layers can be realized on sapphire substrates through monolayer h-BN.The field of sapphire can only partially penetrate the bilayer h-BN and result in the mixing of remote epitaxy and van der Waals(vdWs)epitaxy.Due to the weak interfacial scattering and high crystalline quality of ZrS_(2) epilayer,the ZrS_(2) photodetector with monolayer h-BN shows the best performance,with an on/off ratio of more than 2×10^(5) and a responsivity up to 379 mA·W^(-1).This work provides an efficient approach to prepare single-crystal transition metal dichalcogenides and their heterojunctions with h-BN,which have great potential in developing large-area 2D electronic devices.

全组分/带隙可调的二维ZrS_(2(1-x))Se_(2x)半导体合金的外延生长及其光电应用

过渡金属硫化物(TMDs)的带隙工程对于拓宽其在电子和光电子器件中的应用具有重要意义.本文中,我们首次报道了通过简单的一步化学气相沉积法在蓝宝石衬底上外延生长大面积、全组分可调的ZrS_(2(1-x))Se_(2x)合金薄膜.ZrS_(2(1-x))Se_(2x)合金表现出优异的单晶性和外延质量,以及均匀的元素分布,其与衬底的外延关系被确定为ZrS_(2(1-x))Se_(2x)(0001)[10-10]//蓝宝石(0001)[11-20].ZrS_(2(1-x))Se_(2x)合金的带隙随组分的变化从1.86到1.15 eV连续可调,且表现出明显的弯曲特性.基于ZrS_(2(1-x))Se_(2x)的光电探测器对可见光具有灵敏的光响应,响应时间约为100μs,随着Se组分的减少,探测器性能显著提高.本工作为合成带隙可调的ZrS_(2(1-x))Se_(2x)合金提供了一种有效方法,为设计基于TMDs的光电器件提供了极大的灵活性.

Epitaxial growth of large area ZrS_(2)2D semiconductor films on sapphire for optoelectronics

Recently,group-IVB semiconducting transition metal dichalcogenides(TMDs)of ZrS_(2) have attracted significant research interest due to its layered nature,moderate band gap,and extraordinary physical properties.Most device applications require a deposition of high quality large-area uniform ZrS_(2) single crystalline films,which has not yet been achieved.In this work,for the first time,we demonstrate the epitaxial growth of high quality large-area uniform ZrS_(2) films on c-plane sapphire substrates by chemical vapor deposition.An atomically sharp interface is observed due to the supercell matching between ZrS_(2) and sapphire,and their epitaxial relationship is found to be ZrS_(2)(0001)[1010]||Al_(2)O_(3)(0001)[1120].The epitaxial ZrS_(2) film exhibits n-type semiconductor behavior with a room temperature mobility of 2.4 cm^(2)·V^(−1)·s^(−1),and the optical phonon is the dominant scattering mechanism at room temperature or above.Furthermore,the optoelectronic applications of ZrS_(2) films are demonstrated by fabricating photodetector devices.The ZrS_(2) photodetectors exhibit the excellent comprehensive performance,such as a light on/off ratio of 106 and a specific detectivity of 2.6×10^(12) Jones,which are the highest values compared with the photodetectors based on other group-IVB two-dimensional TMDs.

Direct growth of hexagonal boron nitride films on dielectric sapphire substrates by pulsed laser deposition for optoelectronic applications

Recently,hexagonal boron nitride(h-BN),an ultra-wide bandgap semiconductor,has attracted considerable atten-tion owing to its excellent properties.In thin films grown on metal catalysts,contamination and damage induced by a transfer process cannot be avoided.Therefore,synthesizing h-BN films on non-catalytic dielectric substrates is desirable for electronic applications.In this study,we demonstrate the direct growth of high-quality h-BN films with a controllable thickness on sapphire substrates by using the pulsed laser deposition(PLD)technique.The effects of the deposition conditions and laser parameters on the growth of the h-BN films are systematically investigated by evaluating their characteristic Raman peaks.Among the various growth parameters studied,the substrate temperature has the greatest influence on the crystalline quality of the h-BN films,and the optimal pres-sure varies depending on the target-substrate distance.The h-BN film grown under optimal conditions exhibits a narrow Raman line width of∼30 cm^(−1),indicating a high crystalline quality.The photodetectors fabricated from the PLD-grown h-BN films exhibit superior deep-ultraviolet detection performance with a large on/offratio of>104,high photoresponsivity,and a sharp cut-offwavelength of 220 nm.This study presents the possibility of producing high-quality h-BN films by applying PLD on dielectric substrates for optoelectronic applications.