[en] Biodegradable magnesium alloys have attracted much attention in recent years due to their potential applications in cardiovascular stents and bone implants. However, their inadequate corrosion resistance in the physiological environment is a major obstacle limiting wider application. In this work, a niobium nitride (NbN) film is deposited on Mg-Y-RE alloy (WE43) by reactive magnetron sputtering to improve the corrosion resistance. The structure of the nitride film is determined by grazing incidence X-ray diffraction and X-ray photoelectron spectroscopy. The corrosion behavior of the uncoated and NbN-coated WE43 is evaluated in simulated body fluids by electrochemical impedance spectroscopy, polarization tests, and immersion tests. The surface morphology of the samples before and after the immersion tests is examined by scanning electron microscopy to assess the degree of corrosion. Our results indicate that the corrosion resistance is improved by the corrosion-resistant nitride film and the reasons are discussed. - Highlights: • Niobium nitride is deposited on magnesium alloy by reactive magnetron sputtering. • Niobium nitride enhances the corrosion resistance in simulated body fluids. • Corrosion products contain mainly Mg, O, and P

[en] The application of silicon-on-insulator (SOI) substrates to high-power integrated circuits is hampered by the self-heating effect due to the poor thermal conductivity of the buried SiO₂ layer. We introduce aluminum nitride (AlN) thin films formed by ultra-high vacuum electron-beam evaporation with ammonia as an alternative. The chemical composition, surface morphology, and electrical properties of these films were investigated. The film synthesized at 800 deg. C shows a high AlN content, low surface roughness with a root-mean-square value of 0.46 nm, and high electrical resistivity. Based on thermodynamic analysis and our experimental results, the mechanism of AlN formation is proposed

[en] Hydrogen plasma immersion ion implantation (PIII) in conjunction with ion-cut has been successfully utilized to fabricate silicon-on-insulator (SOI) wafers. In order for PIII to be accepted by the semiconductor industry as a commercial process, surface metal contamination that can affect device yield and properties must be minimized. Total-reflection X-ray fluorescence (TXRF) analysis of hydrogen PIII silicon wafers reveals surface iron contamination to be greater than 10¹² atoms/cm². Even though ions bombard all surfaces in a PIII chamber and the sample stage is made of stainless steel, the small sputtering yield by hydrogen cannot fully account for the surface iron on the wafer. Further studies reveal that the sputtering contribution of ionized atmospheric species in the residual vacuum is significant. To minimize metal contamination in hydrogen PIII, the gas lines must be designed and sealed properly as outside air can easily leak into vacuum chamber due to the negative pressure inside the gas line

[en] We have investigated the electrostatic charging effects of dielectric substrate materials during plasma immersion ion implantation. The results demonstrate that the time-dependent surface potential (negative) may be reduced in magnitude due to the charging effect of the dielectric surface, leading in turn to a reduction in the energy of the incident ions and a broadening of the implanted ion energy spectrum. The charging effect is greater during the plasma immersion bias pulse rise-time, and the electrostatic potential charging may be as large as 75% of the total applied (pulse) potential. This is due to abundant charge movement both of ions and secondary electrons, and has been confirmed by computer simulation. The plasma sheath capacitance has a small influence on the surface potential, via the bias pulse rise-time. Processing parameters, for example voltage, pulse duration, plasma density, and pulse rise-time, have a critical influence on the charging effects. Short pulse duration, high pulse frequency and low plasma density are beneficial from the viewpoint of maximizing the implantation ion energy

[en] The damage and defects created in silicon by hydrogen plasma immersion ion implantation (PIII) are not the same as those generated by conventional beamline ion implantation due to the difference in the ion energy distribution and lack of mass selection in PIII. Defect generation must be well controlled because damage in the implanted and surface zones can easily translate into defects in the silicon-on-insulator structures synthesized by the PIII/wafer bonding/ion-cut process. The defect formation and its change with annealing temperature were investigated experimentally employing channeling Rutherford backscattering spectrometry, secondary ion mass spectrometry, and atomic-force microscopy. We also calculated the damage energy density of the three dominant hydrogen species in the plasma (H⁺, H₂⁺, and H₃⁺) as well as displacement of silicon atoms in the silicon wafer. H₂⁺ creates the most damage because its damage energy density is very close to the silicon threshold energy. The effects of atmospheric gaseous impurities unavoidably coimplanted from the overlying plasma are also modeled. Even though their concentration is usually small in the plasma, our results indicate that these gaseous impurities lead to significant silicon atom displacement and severe damage in the implanted materials. copyright 2001 American Institute of Physics

[en] Highlights: • Carbon, as a biocompatible benign element, was implanted into Mg. • A protective amorphous carbon layer was formed after implantation. • Treated sample exhibits good corrosion resistance in two solutions. - Abstract: The corrosion resistance of magnesium-based biomaterials is critical to clinical applications. In this work, carbon as a biocompatible and benign nonmetallic element with high chemical inertness is implanted into pure magnesium to improve the corrosion behavior. X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HR-TEM), and Raman scattering reveal the formation of an amorphous carbon layer after ion implantation. Electrochemical studies demonstrate remarkable improvement in the corrosion resistance of magnesium in simulated body fluids (SBF) and Dulbecco’s Modified Eagle Medium (DMEM)

[en] Plasma immersion ion implantation (PIII) is conducted to improve the intrinsically poor corrosion properties of biodegradable AZ31 magnesium alloy in the physiological environment. Carbon dioxide is implanted into the samples and X-ray photoelectron spectroscopy and scanning electron microscopy are used to characterize the materials. The corrosion properties are systematically studied by potentiodynamic polarization tests in two simulated physiological environments, namely simulated body fluids and cell culture medium. The plasma-implanted materials exhibit a lower initial corrosion rate. Being a gaseous ion PIII technique, conformal ion implantation into an object with a complex shape such as an orthopedic implant can be easily accomplished and CO₂ PIII is a potential method to improve the biological properties of magnesium and its alloys in clinical applications.

[en] Plasma immersion ion implantation (PIII) is an established technique in certain niche microelectronics applications such as the synthesis of silicon-on-insulator. In other applications such as shallow junction formation by plasma doping, trench doping, and fabrication of blue light emitting materials, PIII has unique advantages over conventional techniques and may be the technique of choice in the future. There have been significant developments in these areas and recent breakthroughs in plasma and trench doping are discussed in this review paper. Results pertaining to direct-current PIII that excels in planar sample processing as well as the optical characteristics of nano-cavities produced by hydrogen PIII are also presented

[en] Although sodium ion implantation is useful to the surface modification of biomaterials and nano-electronic materials, it is a challenging to conduct effective sodium implantation by traditional implantation methods due to its high chemical reactivity. In this paper, we present a novel method by coupling a Na dispenser with plasma immersion ion implantation and radio frequency discharge. X-ray photoelectron spectroscopy (XPS) depth profiling reveals that sodium is effectively implanted into a silicon wafer using this apparatus. The Na 1s XPS spectra disclose Na₂O–SiO₂ bonds and the implantation effects are confirmed by tapping mode atomic force microscopy. Our setup provides a feasible way to conduct sodium ion implantation effectively.

[en] The use of tantalum pentoxide (Ta₂O₅) thin films as advanced gate dielectrics in integrated circuits has been hampered by thermodynamic instability at the Ta₂O₅/Si interface. We have demonstrated the fabrication of crystalline Ta₂O₅ thin films on n-type Si (100) at lower substrate temperature by means of substrate biasing. In the work reported here, the influence of the substrate bias on the interfacial and dielectric characteristics of the Ta₂O₅ thin films is investigated in details. Our results show that by applying a suitable bias to the Si substrate, the dielectric properties of Ta₂O₅ thin films can be improved. Using a substrate bias of -200 V, the thin film has a permittivity of 34 and leakage current density of 10^-7 A/cm² at an electric field of 800 kV/cm. The effects and mechanism of the bias on the interfacial and dielectric characteristics are described