N-polar GaN上的欧姆接触:材料制备、金属化方案与机理

氮极性(N-polar)GaN与镓极性(Ga-polar)GaN极性相反,且具有较高的表面化学活性,使其在光电子、微电子及传感器等领域逐渐受到关注。文章结合一些相关研究报道,综述了N-polar GaN上欧姆接触的研究进展。首先对N-polar GaN材料的制备进行了分析,随后对N-polar GaN的欧姆接触电极的金属化方案及欧姆接触机理等内容进行了综合讨论,以期为实际N-polar GaN欧姆接触研究提供一些参考。     

GaN纳米线材料的特性和制备技术

GaN是一种具有优越热稳定性和化学性质的宽禁带半导体材料,这种材料及相关器件可以工作在高温、高辐射等恶劣环境中,并可用于大功率微波器件．最近几年,由于GaN蓝光二极管的成功研制,使GaN成为了化合物半导体领域中最热门的研究课题．简要介绍了GaN纳米线材料的制备技术;综述了GaN纳米线材料的制备结果和特性．用CVD法研制的GaN纳米线的直径已经达到5～12nm,长度达到几百个微米．纳米线具有GaN的六方纤锌矿结构,其PL谱具有宽的发射峰,谱峰中心在420nm．GaN纳米线已经在肖特基二极管的研制中得到应用．     

ZnO nanowire arrays as substrates for cell proliferation and differentiation

In the latest years, the use of zinc oxide (ZnO) nanostructures has been proposed in different biomedical applications, however, to date, only a few contrasting results concerning their biocompatibility can be found in the literature. In particular, the application of the extraordinary piezoelectric properties of ZnO nanostructures has poorly been explored for the culture of electrically excitable cells, and, for this reason, systematic investigations of their interactions with these living systems appear to be necessary. In this paper, we report about adhesion, proliferation and differentiation of two mammalian cell lines (PC12, as model of neuronal cells, and H9c2, as model of muscle cells) over ZnO nanowire arrays. We demonstrate suitability of these arrays in sustaining cellular functions, and their potential in applications that range from tissue engineering to minimally invasive sensing and/or stimulation.     

以SiCl4/H2为气源低温制备pc-Si薄膜的稳恒光电导特性

研究了以SiCl4/H2为气源、用等离子体增强化学气相沉积方法, 在低于300℃温度下所制备的pc-Si薄膜在长时间的光照下电导率的变化情况.实验结果表明,所制备的多晶硅薄膜具有类稳恒光电导效应,而且薄膜的稳恒光电导特性依赖于薄膜的晶化率和晶粒尺寸,随晶化率的增加和晶粒尺寸的增大而增大.     

Magnetic Properties of (Ga,Fe)N

Wurtzite (Ga,Fe)N bulk crystals were, for the first time, successfully grown by AMMONO and chemical transport methods. The magnetization measurements of (Ga,Fe)N crystals revealed the coexistence of paramagnetic and ferromagnetic contributions. The paramagnetic component was shown to be growth condition dependent. The Brillouin-type behavior was observed in the samples obtained by both methods. Some (Ga,Fe)N samples (especially those codoped with Si) grown by the chemical transport method show a Van Vleck–type paramagnetic behavior.     

DRIFTS characterization of a nanostructured gallium nitride powder and its interactions with organic molecules

Nanoparticles of gallium nitride, which are of great interest in optical technology, were synthesized and characterized. The surface chemical composition of these nanoparticles, which can affect the overall properties of the material, was analyzed by diffuse reflectance Fourier transform infrared spectrometry. The interaction of the GaN first atomic layer with acetic acid was investigated as a preliminary step for the deagglomeration study of the nanoparticles in polymer matrixes.     

Neuroactive conducting scaffolds: nerve growth factor conjugation on active ester-functionalized polypyrrole

Electrically conductive and biologically active scaffolds are desirable for enhancing adhesion, proliferation and differentiation of a number of cell types such as neurons. Hence, the incorporation of neuroactive molecules into electroconductive polymers via a specific and stable method is essential for neuronal tissue engineering applications. Traditional conjugation approaches dramatically impair conductivities and/or stabilities of the scaffolds and ligands. In this study, we developed copolymers (PPy-NSE) of N-hydroxyl succinimidyl ester pyrrole and regular pyrrole, which can be immobilized with nerve growth factor (NGF) without significantly hindering electroconductivity. The presence of active ester groups was confirmed using reflectance infrared spectroscopy and X-ray photoelectron spectroscopy (XPS) from the copolymers prepared from different monomer compositions. We selected PPy-NSE₅₀ (polymerized from a 50 : 50 monomer ratio of pyrrole : pyrrole-NSE) for further modification with NGF because this copolymer retains good conductivity (approx. 8 S cm⁻¹) and presents active ester groups for NGF immobilization. We tethered NGF on the PPy-NSE₅₀ surface, and found that PC12 cells extended neurites similarly to cells cultured in NGF-containing medium. XPS and enzyme-linked immunosorbent assay confirmed that NGF immobilized via the active ester on the PPy-NSE₅₀ film was stable for up to 5 days in phosphate-buffered saline solution. Also, application of an external electrical potential to NGF-immobilized PPy films did not cause a significant release of NGF nor reduce their neurotrophic activity. This novel scaffold, providing electroconductive and neurotrophic activities, has potential for neural applications, such as tissue engineering scaffolds and biosensors.