Papers by Keyword: Surface Conditioning

Abstract: In this paper, we study high-temperature H₂, N₂, and H₂/N₂ surface conditioning processes prior to the SiO₂ deposition as a promising approach for SiO₂/4H-SiC interface preparation in metal-oxide-semiconductor field-effect transistors (MOSFET). A thorough electrical analysis is presented, consisting of temperature-dependent transfer characteristics as well as reliability studies regarding bias temperature instabilities (BTI) and dielectric breakdown behavior. Especially N₂-containing surface pretreatments were found to greatly suppress electron traps, whereas hole trapping is enhanced. Finally, X-ray photoelectron spectroscopy (XPS) was utilized to elucidate the elemental surface composition after the different annealing procedures. The obtained results are in good agreement with the electrical characterization and complement already published results regarding the formation of surface reconstructions on 4H-SiC through H₂ and H₂/N₂ annealings.

Abstract: This paper presents an experimental investigation of the mechanical response and failure mode of magnesium alloy-based Fibre Metal Laminates (FMLs) having different surface pretreatments under axial compression loading conditions. To improve the interfacial bonding strength between the metal and composite layers, three categories of samples were fabricated by hot pressing using sandblasted, annealed and both sandblasted and annealed AZ31B magnesium alloy sheets. To evaluate the bonding strength along the shear and normal directions, single lap shear tests and T-peel tests were conducted. It was found that the combination of sandblasting and annealing can greatly enhance the shear and normal interfacial bonding strength compared with only sandblasting and annealing, separately. To assess the effect of the interfacial bonding strength on the FML compressive performance, quasi-static buckling tests were performed at varying surface treatments of the magnesium alloy sheets. The analysis of the load-stroke curves and failure modes indicates that delamination can significantly reduce the buckling capability and structural stability, and that the improvement of interfacial bonding strength can dramatically strengthen the FML compressive capability.

Abstract: Ultrapure water (UPW) is widely used for rinsing wafers and diluting chemicals in semiconductor manufacturing processes. The quality of UPW is severely controlled, but the generation of hydrogen peroxide (H₂O₂) as a impurity is inevitable due to the ultraviolet irradiation in a UPW production system (Figure 1). In our survey, it is revealed that the concentration of H₂O₂ in UPW reaches to 10~40 μg/L level. Considering the situation, we have developed a palladium-loaded monolithic anion exchange resin (Pd-M) as a catalyst that is able to remove H₂O₂ from UPW down to below 1 μg/L at an extremely high flow rate (space velocity SV = 6,000 h^-1), with no detectable elution of impurities [1, 2]. Furthermore, we have found that the dissolution rate of copper which is easy to be corroded oxidatively in CO₂-dissolved water (CO₂ UPW) [3] can be decreased to one-third by removal of H₂O₂ from CO₂ UPW using Pd-M catalyst [4]. In this study, we present the effects of H₂O₂ removal from UPW and diluted hydrofluoric acid (DHF) on the surfaces of copper, molybdenum and silicon.

Abstract: As a high-efficiency silicon solar cell concept amorphous silicon/crystalline silicon (a-Si:H(n,p)/c-Si (p,n)) hetero-junction solar cells are of great scientific interest [1, . The a-Si:H emitter is deposited by plasma-enhanced chemical vapor deposition (PECVD). The biggest challenge is to avoid recombination at the a-Si:H(i)/c-Si interface where the p-n junction is located. A clean, smooth, hydrogen terminated c-Si surface is supposed to be mandatory for a high passivation quality of the deposited layer [3, 4]. It is well established that treatment in dilute hydrofluoric acid (dHF) solution (1-10%) produces a hydrogen-terminated, clean Si surface [e.g. 5, 6, 7]. H-termination is supposed to rise with increasing etch time [8]. Whereas prolonged rinsing after the etch step leads to a formation of OH-groups at the surface [8]. Because of the high sensitivity of the a-Si:H(i)/c-Si interface the influence of prolonged etching in dHF (1%) as well as prolonged rinsing in deionized water (DI water) on the passivation quality of the deposited a-Si:H(i) layer has to be carefully studied. Also the possibility of decreased hydrophobicity and a possible iron recontamination from the HF has been taken into account.

Abstract: Emitter formation of crystalline silicon solar cells by inline diffusion can be affected by non-uniformities in dopant deposition prior to the furnace due to insufficient wetting of hydrophobic surfaces. The impact of dissolved ozone treatment after texturing has been investigated with respect to the possibility of improving the emitter formation with a low cost process enhancement. The chemically grown thin oxide improves wetting capability without modification of other surface characteristics that can impact cell efficiency. It could be shown that already low concentrations of ozone in UPW prior to phosphorus doping improve the sheet resistance uniformity on Cz-Si and multi-crystalline Si solar cells between 30 and 100 % compared to HF last treated ones.

Abstract: The purpose of treatment for peri-implantitis is to achieve structural and functional restoration of the lost supporting tissues around implants, including re-osseointegration. Both surgical and non-surgical approaches in combination with a variety of anti-microbial treatment regimens have been applied depending on the size and shape of the bone defect. Tetracycline-HCl (Tc) treatment has been considered as a effective chemical modality for decontamination and detoxification of contaminated implant surfaces. The aim of this study was to examine if Tc conditioning changes the microstructures of the modified surface of dental implants. Dental implants with (1) hydroxyapatite-coated surface (HAS) (Replace® select HA, Nobel Biocare AB, Göthenburg, Sweden), (2) TiO2-blasted surface (TBS) (Astra TiOblast®, ASTRA Tech AB, Mölndal, Sweden) were used in this study. Tc treatment noticeably altered the surface of HAS and TBS. HAS and TBS were partially removed from the implant surface as early as 90 and 60 sec, respectively.

Abstract: The increased surface roughness of dental implants has shown enhanced integration of bone tissues to implant surfaces, but may be predisposed to an increased risk of pathogenic bacterial infection and contamination with bacterial products. Tetracycline-HCl (Tc) treatment has been regarded as a practical and effective chemical modality for decontamination and detoxification of contaminated implant surfaces. The purpose of this study was to examine if Tc treatment alters the microstructures of the modified surface of dental implants. For this purpose, dental implants with pure titanium machined surface (MS), sandblasted, large grit, acid-etched surface (SLAS), or anodized surface (AS) were used. The surface of dental implants was rubbed for 30, 60, 90, 120, or 150 sec with sponge pellets soaked in Tc solution (50mg/ml) and in distilled water for 0 and 150 sec as the control group. The specimens were then routinely processed for scanning electron microscopy. The results show that Tc treatment did not change the surface of MS, SLAS, and AS.

Abstract: Osseointegrable surgical implants are usually made on titanium or titanium alloys. The osseointegration process is improved by surface conditioning of these implants, increasing surface area with no loosing of bio-compatibility, i.e., without contamination by non bio-compatible materials. The surface conditioning of these implants might be accomplished in different ways: blasting, chemical etching, deposition, etc. Two alternatives considering titanium powders are discussed in this work: blasting and plasma spraying deposition. Results are presented in terms of topography of osseointegrable surgical implants through scanning electron microscopy techniques.