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In this study, BSi cluster ions of 77 keV and B monomer ions of 22 keV were respectively implanted into silicon wafers at room temperature and geometrically tilted. Rapid thermal annealing of the as-implanted specimens at 1050 °C for 25 s was also employed. The results revealed that all the as-implanted and as-annealed range parameters (Rp, ΔRp, γ, β and ΔRt) of the BSi cluster ion implantation are smaller than those of the B monomer ion implantation. The as-annealed range parameters are larger than the as-implanted ones for both the BSi cluster ion and the B monomer ion implantations mainly due to radiation enhanced diffusion (RED) effects. RED effects also tend to drive boron atoms out-diffusion towards the specimen surface. However, the SiO2 layer at the surface acts as a diffusion barrier by which it traps boron atoms nearby. The existence of larger amounts of defects explains the presence of a more pronounced accumulation of out-diffused boron atoms in the as-annealed boron depth profile of the BSi cluster ion implantation compared to that of the B monomer ion implantation. [Copyright &y& Elsevier]

Neutron transmutation doping (NTD) has demonstrated its initial feasibility in offering precisely controlled and highly uniform dopants within bulk gallium nitride (GaN) wafers. This study aims to assess the doping efficacy of NTD applied to heteroepitaxial GaN films and address the technical challenges related to neutron damage and impurity activation through a comprehensive investigation of neutron irradiation parameters and annealing temperatures. Heteroepitaxial GaN films on sapphire were exposed to neutrons with varying thermal to fast neutron flux ratios in a fission reactor. The results highlight the successful application of the NTD process to heteroepitaxial GaN films, utilizing a relatively harder neutron spectrum with nearly equal thermal and fast neutron fluxes. Notably, a significant activation yield of 95.4 % was achieved through annealing at 1100 °C. Furthermore, the lattice damage and electrical conduction properties of heteroepitaxial GaN films show a strong correlation with the fast neutron fluence and annealing temperature. Elevated annealing temperature promotes the recovery from neutron-irradiated damage and enhances the activation of transmuted dopants. However, some residual defects still persist in neutron-irradiated GaN crystal after annealing. The outcomes of this study are expected to be useful for the establishment of optimal process parameters for NTD-GaN. [ABSTRACT FROM AUTHOR]

To suppress the electric-field crowding at the edge of GaN-based power devices and enhance the breakdown voltage as well, argon ion (Ar+) implantation has been demonstrated an efficient process of edge termination for n-type GaN, that is realized by the introduction of radiation-induced defects to modify electric-field distribution around the edge of devices. However, a high fluence of Ar+ irradiation inevitably causes radiation damage, which is absolutely detrimental to the electrical and material properties of GaN crystal. Therefore, the purpose of this study is to investigate the effects of radiation damage arising from Ar+ implantation on n-type GaN epitaxial layer. 180 keV Ar ions with various fluences ranging from 4.8 × 1013 to 6 × 1015 cm−2 were implanted, forming a thin damaged area near the surface of GaN epitaxial layer. The characteristics of Ar+-implanted GaN epitaxial layer were then thoroughly investigated by Hall effect measurement, X-ray diffraction (XRD), photoluminescence (PL), and Raman scattering spectroscopy. The results indicated that the electron concentration of GaN decreases with the increase of Ar+ fluence. About 32.5 % of carriers in GaN are removed after Ar+ irradiation to a maximum fluence of 6 × 1015 cm−2. As revealed by PL spectra, Ar+ implantation-induced defects would trap free carriers and behave like non-radiative recombination centers. An abrupt increase in lattice strain derived from XRD spectra implies a localized amorphous layer that may be formed in GaN crystal when Ar+ fluence is higher than 1.2 × 1015 cm−2. The Raman spectra also evidenced that Ar+ implantation into GaN leads to N sublattice damage and degradation in electrical conduction properties. The results obtained in this study are expected to be useful for the design of Ar+-implanted edge termination for GaN power devices. [ABSTRACT FROM AUTHOR]

In recent years, gold (Au) nanoparticles have been synthesized via various methods and used in optical and biomedical detection. Au nanoparticles contain some remarkable dimension-dependent optical properties due to surface plasmon resonance (SPR) in Au nanoparticles which causes high absorption in visible light regions. Since SPR in well-crystallized Au nanoparticles can enhance the local electromagnetic field, it is thus expected that greater efficiency in the photoluminescence (PL) originating from oxygen deficiency centers (ODC) can be achieved in Au-implanted SiO 2 matrix. In order to demonstrate the enhancement of PL, Au nanoparticles were formed in SiO 2 film using ion beam synthesis and their optical and microstructural properties were also investigated in this study. The results revealed that a clear absorption peak at approximately 530 nm was identified in the UV-Vis spectra and was attributed to SPR induced by Au nanoparticles in SiO 2 . The SPR of Au nanoparticles is also dependent on thermal treatment conditions, such as post-annealing temperature and ambient. The Au nanoparticle-containing SiO 2 film also displayed several distinctive peaks at approximately 320, 360, 460, and 600 nm in the PL spectra and were found to be associated with ODC-related defects and non-bridging oxygen hole centers (NBOHC) in SiO 2 . In addition, the PL peak intensities increased as post-annealing temperature increased, a finding contradictory to the defect recovery but highly consistent with the SPR tendency. A maximum PL emission was achieved when the Au-implanted SiO 2 film was annealed at 1100 °C for 1 h under N 2 . Therefore, the existence of Au nanoparticles in SiO 2 film can induce SPR effects as well as enhance PL emission resulting from defect-related luminescence centers. [ABSTRACT FROM AUTHOR]

The mechanisms of photoluminescence (PL) originating from Si + /C + implanted SiO 2 are still unclear and need to be clarified. Thus, the purpose of this study is to thoroughly investigate the effects of ion implantation and post-annealing temperature on microstructures and PL characteristics of the Si + /C + implanted SiO 2 films. A comparative analysis was also conducted to clarify the different optical properties between the Si + and Si + /C + implanted SiO 2 films. In this study, thermally-grown SiO 2 films on Si substrates were used as the matrix materials. The Si + ions and C + ions were separately implanted into the SiO 2 films at room temperature. After ion implantation, the post-annealing treatments were carried out using the furnace annealing (FA) method at various temperatures (600–1100 °C) for 1 h in a N 2 ambient. The PL characteristics of the implanted SiO 2 films were analyzed using a fluorescence spectrophotometer. The results revealed that the distinct PL peaks were observed at approximately 310, 450 and 650 nm in the Si + -implanted SiO 2 films, which can be attributed to the defects, the so-called oxygen deficiency centers (ODCs) and non-bridging oxygen hole centers (NBOHCs), in the materials. In contrast to the Si + ion implantation, the SiO 2 films which were sequentially implanted with Si + and C + ions and annealed at 1100 °C can emit white light corresponding to the PL peaks located at around 420, 520 and 720 nm, those can be assigned to the Si–C bonding, C–C graphite-like structure (sp 2 ), and Si nanocrystals, respectively. Moreover, a correlation between the optical properties, microstructures, and bonding configurations of the Si + /C + implanted SiO 2 films was also established in this study. [ABSTRACT FROM AUTHOR]