射频等离子体分子束外延GaN的极性研究

对采用射频等离子体分子束外延（RF-plasma MBE)生长得到的GaN进行极性研究。由于镓极性（Ga-polar)比氮极性（N－polar)有更好的化学稳定性，通过比较RF－plasma MBE生长得到的不同GaN样品对光辅助湿法刻蚀的稳定性，发现缓冲层生长条件对GaN外延层的极性有着重要影响：较高缓冲层生长温度得到的GaN外延层表现为N－polar，较低缓冲层生长温度得到的GaN外延层表现为Ga-polar。     

Synthesis and characterization of thin films of poly(3-methyl thiophene) by rf-plasma polymerization

To facilitate synthesis of poly(3-methyl thiophene) thin film by RF-plasma polymerization process, suitable modifications have been done in a RF-sputtering set up. The deposition rate is found to be 3.33 nm/min. The synthesized films are characterized by FTIR, XRD, Ellipsometry, UV-Visible absorption spectroscopy and SEM. From FTIR, the formation of poly(3-methyl thiophene) has been confirmed. It is found that the synthesized polymer is cross-linked. XRD shows the amorphous nature of the prepared polymer film. The optical band gap has been estimated to be 2.14 eV from UV-visible absorption spectrum. Thickness of the polymer films has been measured to be 2000 Å by ellipsometry.     

(Ga,Mn)N : Sn Epilayers

We have prepared (Ga,Mn)N : Sn epilayers on sapphire(0001) substrates by RF-plasma assisted molecular beam epitaxy. We found that codoping with Sn enhances the incorporation of Mn into a GaN host crystal. With increasing the Sn content, the offset ferromagnetic magnetization component tends to disappear and the epilayers become completely paramagnetic. The effective spin number is S 2.5 without Sn, whereas it decreases to S 2.0 when Sn is incorporated. n-type conduction starts to take place when Sn contents exceed beyond the Mn contents.     

常温下采用射频等离子体法合成碳化硅膜

采用射频等离子体增强的气相沉积法，以硅烷和乙烯为原料，在常温下成功的合成了碳化硅薄膜。对于该条件下合成的碳化硅薄膜的结构特征，采用SEM、TEM、XRD、IR等手段进行了分析；分析结果表明我们的样品是以碳硅键为主的薄膜。     

高频等离子体气相反应合成氮化硅超细粉系统的热力学分析

本文采用Solgasmix-PV计算机程序计算了气相反应合成氮化硅超细粉的Si-N-H-Cl四元系的多相平衡。从理论上考察了温度、氮气、氢气、氨气流量对平衡时氮化硅摩尔数的影响。 本文还介绍了依据热力学分析,用高频N_2等离子体作为热源,NH_3、H_2、SiCl_4为反应气体合成Si_3N_4粉末的实验结果。高压电镜观察表明粉末粒度小于0.μm。化学分析测出的粉末组成为:N>37、O<3,C<0.1,Fe<0.01、Al<0.01、Ca<0.01、Mg<0.01(wt％)。粉末呈白色,非晶态。     

Platinum-free counter electrodes of plasma-modified hybrid nanomaterials for dye-sensitised solar cells

Molybdenum disulphide (MoS₂) nanotube and tungsten oxide (W₁₈O₄₉) nanowire were coated with poly(3-hexylthiophene) (P3HT) and poly(3,4-ethylenedioxythiophene) (PEDOT) by a radio frequency (RF: 13.56?MHz)-rotating plasma-modification method as alternative counter electrodes for dye-sensitised solar cells (DSSCs). Surface analysis showed the homogenous plasma nanocoating of inorganic nanostructures by P3HT and PEDOT. It was demonstrated that the plasma-modified hybrid platinum-free counter electrodes increased the efficiencies of the DSSCs. The DSSCs based on hybrid nanostructure materials showed a short circuit current density of 9.49, 7.95, 2.59 and 2.57?mAcm^?2 for MoS₂/P3HT, MoS₂/PEDOT, W₁₈O₄₉/PEDOT and W₁₈O₄₉/P3HT samples, respectively. The plasma nanocoating with the nanostructured materials approach for obtaining hybrid counter electrodes in the photovoltaic action shows an alternative route towards cost-effective, green energy conversion.