Thickness Impact on the Morphology, Strain Relaxation and Defects of Diamond Heteroepitaxially Grown on Ir/Al2O3 Substrates

This paper investigates the formation and propagation of defects in the heteroepitaxial growth of single-crystal diamond with a thick film achieving 500 µm on Ir (001)/Al2O3 substrate. The growth of diamond follows the Volmer–Weber mode, i.e., initially shows the islands and subsequently coalesces to closed films. The films’ strain imposed by the substrate gradually relaxed as the film thickness increased. It was found that defects are mainly located at the diamond/Ir interface and are then mainly propagated along the [001] direction from the nucleation region. Etching pits along the [001] direction formed by H2/O2 plasma treatment were used to show defect distribution at the diamond/Ir/Al2O3 interface and in the diamond bulk, which revealed the reduction of etching pit density in diamond thick-film surface. These results show the evident impact of the thickness on the heteroepitaxially grown diamond films, which is of importance for various device applications.

Improving Device Characteristics of Dual-Gate IGZO Thin-Film Transistors with Ar–O2 Mixed Plasma Treatment and Rapid Thermal Annealing

In this study, high-performance indium–gallium–zinc oxide thin-film transistors (IGZO TFTs) with a dual-gate (DG) structure were manufactured using plasma treatment and rapid thermal annealing (RTA). Atomic force microscopy measurements showed that the surface roughness decreased upon increasing the O2 ratio from 16% to 33% in the argon–oxygen plasma treatment mixture. Hall measurement results showed that both the thin-film resistivity and carrier Hall mobility of the Ar–O2 plasma–treated IGZO thin films increased with the reduction of the carrier concentration caused by the decrease in the oxygen vacancy density; this was also verified using X-ray photoelectron spectroscopy measurements. IGZO thin films treated with Ar–O2 plasma were used as channel layers for fabricating DG TFT devices. These DG IGZO TFT devices were subjected to RTA at 100 °C–300 °C for improving the device characteristics; the field-effect mobility, subthreshold swing, and ION/IOFF current ratio of the 33% O2 plasma–treated DG TFT devices improved to 58.8 cm2/V·s, 0.12 V/decade, and 5.46 × 108, respectively. Long-term device stability reliability tests of the DG IGZO TFTs revealed that the threshold voltage was highly stable.

Low Temperature Hydrophilic SiC Wafer Level Direct Bonding for Ultrahigh-Voltage Device Applications

SiC direct bonding using O2 plasma activation is investigated in this work. SiC substrate and n− SiC epitaxy growth layer are activated with an optimized duration of 60s and power of the oxygen ion beam source at 20 W. After O2 plasma activation, both the SiC substrate and n− SiC epitaxy growth layer present a sufficient hydrophilic surface for bonding. The two 4-inch wafers are prebonded at room temperature followed by an annealing process in an atmospheric N2 ambient for 3 h at 300 °C. The scanning results obtained by C-mode scanning acoustic microscopy (C-SAM) shows a high bonding uniformity. The bonding strength of 1473 mJ/m2 is achieved. The bonding mechanisms are investigated through interface analysis by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). Oxygen is found between the two interfaces, which indicates Si–O and C–O are formed at the bonding interface. However, a C-rich area is also detected at the bonding interface, which reveals the formation of C-C bonds in the activated SiC surface layer. These results show the potential of low cost and efficient surface activation method for SiC direct bonding for ultrahigh-voltage devices applications.

Non-Thermal O2 Plasma Efficacy on C. albicans and Its Effect on Denture Base Resin Color

Denture stomatitis is a disease involving C. albicans, which can affect elderly and immuno-compromised people. To avoid any recurrence of this pathology, it is necessary to treat patients regularly and disinfect dentures. However, the denture cleansers’ efficacy is not optimal and often leads to adverse color effects on the denture base resins. The aim of this study was to investigate the efficacy of a low-pressure non-thermal O2 plasma (NTP) treatment on C. albicans seeded on ProBase®Hot resin (Ivoclar Vivadent). The viability reduction of C. albicans was assessed by colony forming units (CFU) analysis and by scanning electron microscopy (SEM). The effect of repeated treatments on the resin color was evaluated by spectrophotometry. The resin samples were placed in a sealed bag in which O2 plasma was generated in low-pressure conditions. The results showed that a 120-min O2 NTP treatment led to a 6-log reduction of C. albicans viability (p < 0.05) and to yeasts’ major alterations observed by SEM. Furthermore, significant slight color changes of the resin (∆E00 = 1.33) were noted only after six plasma treatments (p < 0.05). However, the denture aesthetic was preserved, as the color changes were not perceptible and remained below the acceptability threshold (∆E00 < 4).

Surface Modification of Bamboo Charcoal by O2 Plasma Treatment and UV-Grafted Thermo-Sensitive AgNPs Hydrogel to Improve Antibacterial Properties in Biomedical Application

With the advancement of science and modern medical technology, more and more medical materials and implants are used in medical treatment and to improve human life. The safety of invasive medical materials and the prevention of infection are gradually being valued. Therefore, avoiding operation failure or wound infection and inflammation caused by surgical infection is one of the most important topics in current medical technology. Silver nanoparticles (AgNPs) have minor irritation and toxicity to cells and have a broad-spectrum antibacterial effect without causing bacterial resistance and other problems. They are also less toxic to the human body. Bamboo charcoal (BC) is a bioinert material with a porous structure, light characteristics, and low density, like bone quality. It can be used as a lightweight bone filling material. However, it does not have any antibacterial function. This study synthesized AgNPs under the ultraviolet (UV) photochemical method by reducing silver nitrate with sodium citrate. The formation and distribution of AgNPs were confirmed by UV-visible spectroscopy and X-ray diffraction measurement (XRD). The BC was treated by O2 plasma to increase the number of polar functional groups on the surface. Then, UV light-induced graft polymerization of N-isopropyl acrylamide (NIPAAm) and AgNPs were applied onto the BC to immobilize thermos-/antibacterial composite hydrogels on the BC surface. The structures and properties of thermos-/antibacterial composite hydrogel-modified BC surface were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared spectrum (FT-IR), and X-ray photoelectron spectroscopy (XPS). The results show that thermos-/antibacterial composite hydrogels were then successfully grafted onto BC. SEM observations showed that the thermos-/antibacterial composite hydrogels formed a membrane structure between the BC. The biocompatibility of the substrate was evaluated by Alamar Blue cell viability assay and antibacterial test in vitro.