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This study investigated the effect of low-temperature heating on internal stresses of SiNx thin films prepared by plasma enhanced chemical vapour deposition. It was found that films deposited at 473 K developed tensile stresses after heating in air to temperatures above 573 K. The stresses increased with increasing heating time and temperature. Heating to above 873 K was found to cause partial apparent...
Room temperature free-exciton emission was observed in stoichiometric ZnO epilayers grown on Al2O3 substrates by pulsed laser deposition. Absorption and photoluminescence measurements clearly showed the free-exciton emissions at 3.30~3.31 eV. This free-exciton recombination results from the high-quality single-crystalline ZnO epilayers. Temperature-dependent excitonic properties revealed the higher...
High resolution Laplace deep level transient spectroscopy (LDLTS) at temperatures up to 450 K has been applied to thin polycrystalline semiconducting diamond films deposited on n-type silicon. Such structures form p-n diodes and can be characterised by capacitance DLTS. The boron doped diamond films were grown by hot filament chemical vapour deposition and the diamond film thickness was 3-4 microns...
In this paper, we present and analyse secondary ion mass spectrometry (SIMS) measurements of oxygen concentration in 3C-SiC epitaxial layers on Si. The concentration of oxygen determined by SIMS was as high as 1019 to 1020 atom/cm3. Unlike silicon, oxygen can act as donor atoms in SiC with calculated ionization levels of 200 meV. It is generally believed that the main contribution of dopant concentration...
A large batch PECVD system has been developed in order to deposit a-Si/a-SiGe and a-Si/muc-Si solar cell on 20 pieces of SnO2-coated glass with the area of 0.8 m2. Newly designed electrode has been used in order to achieve uniform muc-Si film on 0.8 m2. Beside muc-Si nlayer, p(muc-SiO) has been used in the p-layer of the bottom cell in order to increase the module performance. Alcohol flush has been...
Polycrystalline Cu(InGa)Se2 (CIGS) thin films have been grown onto a soda-lime glass substrate by the co-evaporation process using ionized Ga. It was found from the XRD and Raman measurements that the crystallinity of the films grown with ionized Ga was equivalent to the films grown with normal Ga. In addition, a reduction of defect densities measured by the admittance spectroscopy and the improvement...
Severe Al/poly-Si contact degradation is observed after metallising p-type BSF (back surface field) layers of poly-Si thin-film diodes on glass which received a hydrogen passivation treatment prior to contact formation. The degradation is confirmed by comparative dark I-V measurements on the hydrogenated and non-hydrogenated samples. Two methods - thermal annealing and Si etching using coloured HF...
We evaluate an ordered organic-inorganic solar cell architecture based on CdS QD-decorated ZnO nanorod arrays encased in the hole-conducting polymer Poly(3-hexylthiophene-2,5-diyl) (P3HT). In this work, CdS quantum dot with different sizes were attached to the surface of the nanorods capped with mercaptopropionic acid. The results show that the CdS QDs on the ZnO nanorods increase both the open circuit...
In this paper, a discussion is made of the design of silicon cells to be used in a six-junction tandem solar cell structure as part of the Very High Efficiency Solar Cell (VHESC) program. Minority carrier recombination at surfaces and in the volume, internal quantum efficiency, resistance losses, free carrier parasitic absorption, optical reflection, light trapping, and light absorption must be traded...
Optimized chemical structure was proposed for boron-doped Si quantum dots superlattices. Boron-doped Si quantum dots superlattices were then synthesized by a co-sputtering technique, and characterized for their promising application in all-Si tandem solar cells. The formation of Si quantum dots was confirmed by transmission electron microscopy. The effect of boron dopant concentration on the Si crystallization...
The semiconductor-passivating layer interfaces, as well as their dielectric properties, play important and very often dominant roles in determining HgCdTe device performance. In this work, photoconductors were fabricated on p-type mid-wave infrared Hg1-xCdxTe material using molecular beam epitaxy (MBE) grown CdTe film as the passivation layer. In order to emphasize the importance of the CdTe passivating...
The structural stability of InAs stacking-fault tetrahedron (InAs-SFT) on GaAs(111) is systematically investigated in terms of strain relaxation by using an empirical potential incorporating electrostatic energy contribution. The InAs-SFT is more stable than coherently grown InAs on GaAs(111) beyond 21 monolayers (MLs), which are comparable with critical film thickness of misfit dislocation generation...
Current-voltage characteristics of 3C-SiC/Si heterojunction diodes are presented with reverse breakdown voltage exceeding 200 V, leakage current of 1.3 mAcm-2 at 200 V, and a +/-1V rectification ratio of 200,000. The reverse leakage current was observed to have both temperature and field dependence and hence a model is presented to explain this observation based on a trap assisted tunneling-thermal...
In this study, the viability of growing a CuInSe2 thin film solar absorber by sputtering using a single target composed of CuSe and InSe powders was investigated. It was found that the ability to obtain a sputtered film with a stoichiometric composition was greatly dependent on the substrate temperature and that the optimum conditions could be obtained by adjusting the sputtering radio frequency power...
Organic photovoltaics (OPVs) have emerged as a potential inexpensive alternative to traditional silicon solar cells. Since the active materials in OPVs can be solution processed, they can be applied at low temperature to flexible substrates, leading to a possible transfer to existing roll-to-roll technology. Present limitations to the technology however, include low power conversion efficiency and...
Nanocrystalline FeSi2 (NC-FeSi2) thin films were grown on Si(111) substrates by facing-targets DC sputtering at room temperature using FeSi2 targets. The NC-FeSi2 films showed hopping conduction behavior, which was confirmed by the temperature dependence of the electric conductivity. n-Type NC-FeSi2/p-type Si and n-type NC-FeSi2/i-Si/p-type Si heterojunctions were prepared to be employed as photovoltaics...
The Al-coated-oxide pyramids have been fabricated with and without Ti wetting layer. The nano-size aperture surrounded by the periodic structure on the fabricated oxide pyramid has been fabricated using focused ion beam milling system. The significantly reduced light transmittance from the Al metal aperture with Ti wetting layer have been measured, and compared it with the sample without Ti layer...
We discuss the role of stress on diffusion of vacancies and interstitials theoretically. The stresses induced by SiO2 and TiO2 dielectric layers on InP and GaAs based QD structures are calculated and some reported quantum dot intermixing results are explained by a stress-induced forced interdiffusion model.
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