Surface treatment of GaN nanowires for enhanced photoelectrochemical water-splitting

High-efficiency hydrogen production through photoelectrochemical(PEC)water splitting has emerged as a promising solution to address current global energy challenges.Ⅲ-nitride semiconductor photoelectrodes with nanostructures have demonstrated great potential in the near future due to their high light absorption,tunable direct band gap,and strong physicochemical stability.However,several issues,including surface trapping centers,surface Fermi level pinning,and surface band bending,need to be addressed.In this work,enhanced photovoltaic properties have been achieved using gallium nitride(GaN)nanowires(NWs)photoelectrodes by adopting an alkaline solution surface treatment method to reduce the surface states.It was found that surface oxides on NWs can be removed by an alkaline solution treatment without changing the surface morphology through X-ray photoelectron spectroscopy(XPS),scanning electron microscopy(SEM)and other characterization methods.These findings provide new insights to the development of high-efficiency photoelectrodes for new energy source applications.

Monolayer graphene/GaN heterostructure photodetector with UV‑IR dual‑wavelength photoresponses

An ultraviolet-infrared(UV-IR)dual-wavelength photodetector(PD)based on a monolayer(ML)graphene/GaN heterostructure has been successfully fabricated in this work.The ML graphene was synthesized by chemical vapor deposition(CVD)and subsequently transferred onto GaN substrate using polymethylmethacrylate(PMMA).The morphological and optical properties of the as-prepared graphene and GaN were presented.The fabricated PD based on the graphene/GaN heterostructure exhibited excellent rectify behavior by measuring the current–voltage(I–V)characteristics under dark conditions,and the spectral response demonstrated that the device revealed an UV-IR dual-wavelength photoresponse.In addition,the energy band structure and absorption properties of the ML graphene/GaN heterostructure were theoretically investigated based on density functional theory(DFT)to explore the underlying physical mechanism of the two-dimensional(2D)/three-dimensional(3D)hybrid heterostructure PD device.This work paves the way for the development of innovative GaNbased dual-wavelength optoelectronic devices,offering a potential strategy for future applications in the field of advanced photodetection technology.

非平整基底上活性剂驱动的液滴铺展稳定性研究

当含有表面活性剂的液滴放置在液膜上时,受表面张力梯度的驱动,液滴会自发向外铺展。在铺展过程中,初始微小扰动会在非线性作用的影响下产生以指进现象为特征的不稳定现象,并与基底几何特征密切相关。基于润滑理论推导的液膜厚度和活性剂浓度演化方程,采用FreeFEM++语言编写数值模拟程序,应用微软MS-MPI运行库进行并行化处理,模拟了非平整基底对含活性剂液滴铺展过程中指进现象的影响,使用功率谱方法分析了不同波数对应的扰动能量增长规律,探究了Marangoni效应、毛细效应与扰动能量间的变化关系,揭露了非平整基底对不稳定性的影响机理。结果表明,非平整基底对手指形貌影响不大,但对手指下游影响明显;不同波数对应的扰动能量存在不同的演化特征,优势波数为20和7;最大扰动能量出现在初始条件设置扰动处,与平整基底相对比,凹槽基底可抑制扰动发展,总扰动能量约为平整基底的80%;波纹基底可促进扰动发展,总扰动能量约为平整基底的105%,且波纹基底在初期对特定波数的扰动有明显的促进作用。总体地,非平整基底通过改变活性剂浓度分布影响扰动能量,进而影响指进现象。