Papers by Keyword: Passivation

Abstract: Interface quality plays a key role in solar cell applications. Interface recombination at the front and rear surfaces, which determine this quality, have significant effects on open circuit voltage and fill factor values. In this work, several surface treatments were applied on Cu(In,Ga)Se₂ (CIGS) surfaces to improve the interface quality. Besides, the passivation layer implementation was investigated to reduce interface recombination between the buffer and absorber layers.

Abstract: Due to the restriction of passive layers containing Cr⁶⁺ [1], which were characterized by excellent corrosion protection due to their self-healing effect for scratches on metal surfaces, current corrosion protection systems consist of chromium (III) -containing thick layer passivation. Due to their lower hardness, current corrosion protection systems are susceptible to mechanical stress. This is particularly critical at barrel plating of screws, rivets etc. where the manufacturing process leads to damages of the corrosion protection layer and consequently to reduced corrosion resistance.To counter this problem, we point out one approach to install hard particles into the passivation layer. The entrapment of the hard particles into the passivation is detected by Glow Discharge Optical Emission Spectrometry. Comparative investigations in the corrosion chamber prove the improvement of the corrosion protection of steel parts with passivation layers containing hard particles.

Abstract: This paper study the effect of scan rates and imposed potential on the growth of the oxide film on the Ti6Al4V alloy surface in acid solution .Polarization curves, plotted at different scan rates show a large range of passivation, with no occurrence of transpassivation . It was found that the scan rate have not a significant effect on the passivation phenomenon. However, it influences the corrosion potential and the current density. Electrochemical impedance spectroscopy results show that the system behaviour is purely capacitive. The increasing trend in transfer resistance, film thickness and the exponent n with the imposed potential is due to the growth of a passive and compact oxide film.

Abstract: In order to evaluate the effect of repeated cleaning on EUV reticles, specifically, on the etched Mo/Si multilayer, wafer-based test structures with a mimic of this etched Mo/Si multilayer (“black-border”) were fabricated. The resistance of Mo and Si towards alkaline chemistries was tested and quantified using these test structures. The initial passivating film on Mo seems to play a role in delaying the Mo to further oxidize and dissolve in alkaline solutions. For the cleaning times used (minutes) the Mo surface, and thus the black-border edges, will probably stay passivated by that protective oxide in alkaline solution (pH 11), with no or only very limited Mo loss. Stirring and the amount of oxygen or other oxidizing species like H2O2 in solution could increase the oxidation rate of the Mo and/or Mo oxides into soluble Mo(VI) species.

Abstract: Copper indium gallium selenide/sulfide (CIGS) and copper zinc tin selenide/sulfide (CZTS) are two thin film photovoltaic materials with many similar properties. Therefore, three new processing steps – which are well-known to be beneficial for CIGS solar cell processing – are developed, optimized and implemented in CZTS solar cells. For all these novel processing steps an increase in minority carrier lifetime and cell conversion efficiency is measured, as compared to standard CZTS processing. The scientific explanation of these effects is very similar to its CIGS equivalent: the incorporation of alkali metals, ammonium sulfide surface cleaning, and Al₂O₃ surface passivation leads to electrical enhancement of the CZTS bulk, front surface and reduced front interface recombination, respectively.

Abstract: Key steps in the fabrication of high-efficiency a-Si:H/c-Si heterojunction solar cells are the controlled pyramid texturing of the c-Si substrates to minimize reflection losses and the subsequent passivation by deposition of a high-quality a-Si:H layer to reduce recombination losses. This contribution reviews our recent results on the optimization of the wet-chemical texturing of crystalline Si wafers for the preparation of heterojunction solar cells with respect to low reflection losses, low recombination losses and long minority carrier lifetimes. It is demonstrated, that by joint optimization of both saw damage etch and texture etch the optical and electronic properties of the resulting pyramid morphology can be controlled. Effective surface passivation and thus long minority charge carrier lifetimes are achieved by deposition of intrinsic amorphous Si ((i) a-Si:H) layers. It is shown, that optimized (i) a-Si:H deposition parameters for planar Si (111) wafers can be transferred to a-Si:H layer deposition on random pyramid textured Si (100) wafers. Statistical analysis of the pyramid size distribution revealed that a low fraction of small pyramids leads to longer minority charge carrier lifetimes and, thus, a higher V_oc potential for solar cells.

Abstract: In Situ gas phase passivation methods can enable new channel materials. Toward this end pure anhydrous HOOH and H2NNH2 membrane gas delivery methods were developed. Implementation led to Si-OH passivation of InGaAs(001) at 350C and Si-N-H passivation of SiGe(110) at 285C. XPS and initial electrical characterization has been carried out. Feasibility for In Situ dry surface preparation and passivation was demonstrated.

Abstract: Aluminum oxide (Al₂O₃) films have been wildly investigated due to the excellent surface passivation for the electrical device. Both hydrogen-terminated and pre-oxidized silicon surfaces were prepared before Al₂O₃ films deposition. Combining chemical environment analysis with the effective minority lifetime data, the effect of the surface conditions on the Al₂O₃ films passivation was discussed. The HF sample with hydrogen-terminated substrate surface had a higher minority carrier lifetime (about 721 μs) than the H₂SO₄+H₂O₂ sample with pre-oxidized substrate surface (about 631 μs). The H atoms played an important role in improving the passivation effect. And the importance of the interfacial oxide layer to Al₂O₃ films passivation was validated too.

Abstract: The influence of thickness of atomic layer deposited Al₂O₃ films on nanotextured fluorescent 6H-SiC passivation is investigated. The passivation effect on the light emission has been characterized by photoluminescence and time-resolved photoluminescence at room temperature. The results show that 20nm thickness of Al₂O₃ layer is favorable to observe a large photoluminescence enhancement (25.9%) and long carrier lifetime (0.86ms). This is a strong indication for an interface hydrogenation that takes place during post-thermal annealing. These result show that an Al₂O₃ layer could serve as passivation in fluorescent SiC based white LEDs applications.

Abstract: Anneals in nitrogen (N) containing atmosphere have been proven as efficient means of improving the channel mobility of SiC MOSFETs. It has been demonstrated that simultaneously the density of interface traps is reduced. However, this process is not yet fully understood. In this study we show a comparison of MOSFETs annealed in different atmospheres and compare their electrically detected magnetic resonance (EDMR) spectra with electrical parameters. We find hints for the N incorporation not only passivating but also creating or transforming defects.