Radiofrequency plasma beam deposition of various forms of carbon based thin films and their characterization

The characteristics of carbonic materials obtained by downstream deposition in a low pressure argon plasma beam injected with acetylene are reported. The influence of substrate temperature, presence of Ni catalyst and hydrogen in gas composition on the material properties is described. By increasing the substrate temperature, an enhanced order in the material is revealed by Raman spectroscopy, while FTIR measurements show a decreasing of the hydrogen content and the disappearing of sp¹ hybridized carbon in the deposit. The SEM and Raman investigation show a clear tendency of crystalline phases formation when hydrogen is assisting the deposition.     

Growth kinetics of low temperature single-wall and few walled carbon nanotubes grown by plasma enhanced chemical vapor deposition

Single-wall, double walled or few walled nanotubes (FWNT) are grown by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) at temperature as low as 600 °C. Most of these structures are isolated and self-oriented perpendicular to the substrate. The growth mechanism observed for single-wall and few walled (less than seven walls) nanotubes is the “base-growth” mode. Their grow kinetics is investigated regarding two parameters namely the growth time and the synthesis temperature. It is shown that nucleation and growth rate is correlated with the number of walls into FWNT. It also provides an evidence of a critical temperature for FWNT synthesis.     

Synthesis and characterisation of hexagonal molybdenum nitrides

Four hexagonal molybdenum nitrides—three modifications of δ-MoN and Mo₅N₆—were prepared by the plasma-enhanced chemical vapour deposition (PECVD) method and ammonolysis of MoCl₅ and MoS₂. The nitrides were structurally characterised by X-ray diffraction, high-resolution transmission electron microscopy, and selected area electron diffraction. δ₁-MoN is best described by the WC-type structure with stacking faults due to nitrogen atom disorder. Ordering of nitrogen atoms results in δ₂-MoN with the NiAs-type structure. Formation of trigonal molybdenum clusters in δ₃-MoN is responsible for the doubling of the unit cell in a and b directions compared to δ₂-MoN. Mo₅N₆ can be viewed as an intergrowth structure of the WC- and NiAs-type building blocks, accompanied by vacancies on Mo sites. Influence of reaction conditions on the formation of the four nitrides is discussed; their magnetic properties are presented.     

PECVD SiC optical waveguide loss and mode characteristics

We report the fabrication of single mode SiC (silicon carbide) waveguides and the measurement of their propagation loss. By studying the effect of sidewalls scattering loss due to surface roughness and by reducing it, minimal propagation loss of 2.3 dB/cm for the TM polarization is measured in the visible at 0.633 μm. This loss can be used as a benchmark for further development of SiC microphotonic components and circuit for sensor systems in harsh environment.     

Structural, chemical and optical features of nanocrystalline Si films prepared by PECVD techniques

The nanostructural and chemical features of nanocrystalline Si (nc-Si) films, which were prepared by plasma-enhanced chemical vapor deposition (PECVD), were investigated in terms of various deposition conditions such as reaction gas fractions and substrate temperature. Such features were related with the photoluminescence (PL) phenomena of the nc-Si films. The phase of the nc-Si films prepared at room temperature is somewhere between amorphous and crystalline states, containing about 2 nm size nanocrystallites, which are well passivated by hydrogen. These films exhibit significant PL intensities near blue light region; the PL peaks shift to lower wavelength with decreasing nanocrystallite size.     

光退火制备多晶硅薄膜的量子态现象

用PECVD法直接沉积的非晶硅(a-Si:H)薄膜在中温情况下光退火,然后用XRD、Raman光谱和SEM分析,发现晶粒大小随退火温度和退火时间呈现量子态现象.平均晶粒大小为30nm左右.     

玻璃衬底上中温制备多晶硅薄膜的量子态现象

用PECVD法直接沉积的非晶硅(a-Si:H)薄膜用传统炉在中温退火,然后用拉曼光谱、XRD和SEM分析,发现晶粒大小随退火温度和退火时间呈现量子态现象.分析发现在传统炉中850℃下退火三个小时晶粒大小出现极大值,平均晶粒尺寸为30nm左右.     

Emitter of hetero-junction solar cells created using pulsed rapid thermal annealing

In this paper, we use a pulsed rapid thermal processing (RTP) approach to create an emitter layer of hetero-junction solar cell. The process parameters and crystallization behaviour are studied. The structural, optical and electric properties of the crystallized films are also investigated. Both the depth of PN junction and the conductivity of the emitter layer increase with the number of RTP pulses increasing. Simulation results show that efficiencies of such solar cells can exceed 15% with a lower interface recombination rate, but the highest efficiency is 11.65% in our experiments.     

Stoichiometry dependent changes in the optical properties and nanoscale track formation of PECVD grown a-SiNx:H thin films upon 100 MeV Au8+ ion irradiation

a-SiN_x:H thin films of different stoichiometry grown by PECVD were subjected to irradiation by 100 MeV Au⁸⁺ ions with various fluences to understand the effect of stoichiometry on properties of thin films upon irradiation. Ellipsometry and UV–Vis study suggest the variation in the refractive index of thin films with fluence. The evolution of Hydrogen due to irradiation is quantified with the help of ERDA. RBS was probed to study the change in thin films' composition upon irradiation, which further helps understand the change in thin films' optical properties. Quenching of photoluminescence in the films with all stoichiometries was also observed due to ion irradiation. X-TEM images show the formation of discontinuous ion tracks of radius 2.5 nm in the film closer to silicon nitride stoichiometry. However, Si rich film does not show the clear formation of tracks. Results are explained in the framework of the Thermal spike mechanism of ion-solid interaction.     

工艺参数对PECVD TiN镀层性能的影响

本文考察了工艺参数对等离子体增强化学气相沉积(PECVD)TiN镀层性能的影响,并且研究了镀层的摩擦学性能与其物理机械性能及结晶学特征之间的关系。结果表明,当N/H比为1、Ti/N比为21、沉积温度为400℃和离化电压为1500V时,镀层具有较好的机械性能及耐磨性能。X—射线衍射分析表明,在本试验条件下所获镀层均为(200)面择优取向。作者指出,要制取理想的TiN镀层,离化电压应不低于1500V,沉积温度必须高于300℃。