Engineering decomposition-resilience and de-coalescence of GaN nanowire ensembles

Self-assembly of well-separated AlN nanowires directly on sputtered metallic TiN films

We demonstrate the self-assembled formation of AlN nanowires by molecular beam epitaxy on sputtered TiN films on sapphire. This choice of substrate allows growth at an exceptionally high temperature of 1180 °C. In contrast to previous reports, the nanowires are well separated and do not suffer from pronounced coalescence. This achievement is explained by sufficient Al adatom diffusion on the substrate and the nanowire sidewalls. The high crystalline quality of the nanowires is evidenced by the observation of near band edge emission in the cathodoluminescence spectrum. The key factor for the lo…

Self-Assembled formation of long, thin, and uncoalesced GaN nanowires on crystalline TiN films

We investigate in detail the self-assembled nucleation and growth of GaN nanowires by molecular beam epitaxy on crystalline TiN films. We demonstrate that this type of substrate allows the growth of long and thin GaN nanowires that do not suffer from coalescence, which is in contrast to the growth on Si and other substrates. Only beyond a certain nanowire length that depends on the nanowire number density and exceeds here 1.5 μm, coalescence takes place by bundling, i.e. the same process as on Si. By analyzing the nearest neighbor distance distribution, we identify diffusion-induced repulsion …

Improved control over spontaneously formed GaN nanowires in molecular beam epitaxy using a two-step growth process

We investigate the influence of modified growth conditions during the spontaneous formation of GaN nanowires on Si(111) in plasma-assisted molecular beam epitaxy. We find that a two-step growth approach, where the substrate temperature is increased during the nucleation stage, is an efficient method to gain control over the area coverage, average diameter, and coalescence degree of GaN nanowire ensembles. Furthermore, we also demonstrate that the growth conditions employed during the incubation time that precedes nanowire nucleation do not influence the properties of the final nanowire ensembl…

硅纳米线、催化生长及电学特性

Silicon Nanowires, Catalytic Growth and Electrical Characterization

名义上未掺杂的硅纳米线（NW）生长的催化化学气相沉积。通过在非晶SiO2、Si 3 N4或结晶Si衬底上使用不同的Au催化剂厚度来优化生长过程以控制纳米线直径。对于SiO2衬底，使用Ar等离子体处理来均匀化催化剂聚结，从而均匀化NW直径。此外，平面场效应晶体管（FET）通过实施10至30 nm薄的名义上未掺杂的Si-NW作为有源区来制造。研究了各种硅化物作为有源区的肖特基势垒源极和漏极接触。对于CoSi、NiSi和PdSi接触，FET的传输特性表现为p型行为。由直径为20纳米、栅长为2.5微米的单个Si-NW组成的FET在1伏偏置电压下提供高达0.15微安的导通电流，并且具有10^7的开/关电流比。这与最近报道的未掺杂Si中的低电导率形成对比。

Radius-Dependent Homogeneous Strain in Uncoalesced GaN Nanowires

We investigate the strain state of ensembles of thin and nearly coalescence-free self-assembled GaN nanowires prepared by plasma-assisted molecular beam epitaxy on Ti/Al$_{2}$O$_{3}(0001)$ substrates. The shifts of Bragg peaks in high-resolution X-ray diffraction profiles reveal the presence of a homogeneous tensile strain in the out-of-plane direction. This strain is inversely proportional to the average nanowire radius and results from the surface stress acting on the nanowire sidewalls. The superposition of strain from nanowires with different radii in the same ensemble results in a broaden…

通过金属去湿实现均匀大面积表面图案化，用于GaN纳米线阵列的自上而下制备

Uniform large-area surface patterning achieved by metal dewetting for the top-down fabrication of GaN nanowire ensembles

本文研究了Pt薄膜去湿形成纳米岛阵列的规律，并以此作为掩模通过干湿法刻蚀自上而下制备GaN纳米线，实现了大面积均匀且尺寸可控的纳米线阵列。

UV Photosensing Characteristics of Nanowire-Based GaN/AlN Superlattices

We have characterized the photodetection capabilities of single GaN nanowires incorporating 20 periods of AlN/GaN:Ge axial heterostructures enveloped in an AlN shell. Transmission electron microscopy confirms the absence of an additional GaN shell around the heterostructures. In the absence of a surface conduction channel, the incorporation of the heterostructure leads to a decrease of the dark current and an increase of the photosensitivity. A significant dispersion in the magnitude of dark currents for different single nanowires is attributed to the coalescence of nanowires with displaced na…

Mo_6S_6纳米线的结构、力学和电学性质

Mo_6S_6 nanowires: structural, mechanical and electronic properties

采用基于密度泛函理论的从头计算方法研究了Mo_6S_6纳米线的性质。分子间形成弱耦合的一维链状结构，如Mo_6Se_6和Mo_6S_（9-x）I_x，晶体的力学和电学性质都是强单轴的。计算出的沿链轴的弹性模量和回弹模量分别为c_（11）= 320 GPa和E_R = 0.53 GPa。电子能带结构和电导率表明Mo_6S_6晶体是良好的准一维导体。在随机相位近似下计算的频率依赖的复介电张量ε，在ε_parallel中显示出强的Drude峰，即，对于平行于链轴极化的电场，以及与带间跃迁相关的几个峰。电子能量损失谱是弱各向异性的，并且在等离子体频率（hbar ω_p）约为20 eV处具有强峰。稳定性分析表明，Mo_6S_6对层状MoS_2的形成是亚稳的。

通过分子束外延在SiO₂/Si衬底上生长的自组装AlN纳米线的结构与光学特性

Structural and optical properties of self-assembled AlN nanowires grown on SiO2/Si substrates by molecular beam epitaxy

本研究通过PAMBE在SiO₂/Si(111)衬底上生长自组装AlN纳米线，表征其结构与光学特性，证实纳米线近乎无应变、结构质量高且光学性能与体材料一致，为相关器件制备提供了材料基础。