T. G. Kim

Electroluminescence mechanism in SiOx layers containing radiative centers

Luminescent silicon oxides containing radiative centers were obtained by using two different techniques. Silicon rich silicon oxides (SRSOs) were fabricated by rf magnetron sputter deposition and Ge-implanted SiO2 films were fabricated by ion implantation following the thermal oxidation of Si. Blue and violet photoluminescence were observed from the SRSO and the Ge-implanted SiO2, respectively. However, the electroluminescence (EL) spectra from both oxides exhibited red and near-infrared luminescence bands. Strong EL was observed only under reverse bias conditions on metal-luminescent oxide–semiconductor structures. The EL intensity and peak position were varied with applied voltages. According to the EL and current–voltage measurements, it is concluded that the possible EL mechanism is the impact ionization of ground state electrons in the radiative centers.

Structural characteristics of Y2O3 films grown on oxidized Si(111) surface

We investigated the characteristics of Y2O3 films grown on an oxidized Si(111) surface, using x-ray diffraction, Rutherford backscattering spectroscopy, and high-resolution transmission electron microscopy. The films grown on the oxidized Si show drastically improved crystallinity, compared with the film grown on clean Si surfaces: channeling minimum yield (Xmin) of 2.5% and full width at half maximum of rocking curve lower than 0.03°. The improvement of the crystallinity was due to the difference of the crystalline structure at the interface between the films grown on the oxidized and clean Si surfaces. Crystalline orientation of Y2O3 islands at the interfacial region was misaligned from the normal substrate direction. The misalignment decreased with increasing the substrate temperature. In particular, the ordering of the oxygen atom in the film grown on oxidized Si was improved compared to that of the Y atom, indicating that the crystallinity of the film is dominantly determined by the arrangement of th...

Modification of magnetic properties of epitaxial Co/Cu multilayers by 1 MeV C+ irradiation

Epitaxial [Co/Cu]10 grown on Si (001) has been irradiated by 1 MeV C+ with a dose of 1×1016/cm2. The intrinsic characteristics of epitaxy, such as crystal structure and fourfold magnetic anisotropy, are conserved after ion irradiation. However, the extrinsic magnetic properties are changed such that the coercivity decreases and the squareness of the hysteresis loop is noticeably improved. The intensity of the Cu (200) peak in the x-ray diffraction pattern increases about three times and its half-width decreases after irradiation. It is concluded that the changes of magnetic properties induced by ion irradiation result from the grain growth and the improved crystalline quality.

Controlling the formation of luminescent Si nanocrystals in plasma- enhanced chemical vapor deposited silicon-rich silicon oxide through ion irradiation

The effect of ion irradiation on the formation of luminescent Si nanocrystals from silicon-rich silicon oxide (SRSO) films deposited by electron cyclotron resonance plasma-enhanced chemical vapor deposition (PECVD) whose Si content ranged from 33 to 50 at. % is investigated. As-deposited SRSO films contained a high density of irregular-shaped Si nanocrystals. Irradiating these films with 380 keV Si at room temperature to a dose of 5.7×1015 cm−2 prior to anneal at 1000 °C is found to increase the luminescence intensity due to Si nanocrystals over the films. Based on the x-ray photoemission spectra and the dependence of the luminescence intensity on the irradiating ion dose, anneal time, and the silicon content of the film, we propose the destruction of pre-existing Si clusters by ion irradiation to be an important factor responsible for the observed enhancement of luminescence, and suggest that preanneal irradiation may be a viable method to control the formation of luminescent Si nanocrystals in PECVD-dep...

Comparison of titanium oxide films grown on bare glass and boiled glass in 50% H2SO4 by metal-organic chemical vapor deposition

Titanium oxide films were deposited on bare glass and boiled glass in 50% H2SO4 for 30 min at various substrate temperatures by metal-organic chemical vapor deposition. We investigated the effects of a substrate temperature between 300 and 550 °C on such properties as thermal stability, deposition rate, and chemical states of the films. The thickness of the films is independent of the substrate treatments. The deposition rate of the films is linearly decreased with increasing substrate temperature. Rutherford backscattering spectroscopy and x-ray photoelectron spectroscopy results indicate that the H2SO4 treated glass substrate is superior to the bare glass substrate in the suppression of out-diffusion of sodium and calcium through the TiO2 film till a substrate temperature of 500 °C. There exist only Ti3+ and Ti4+ oxidation states in the film regardless of a substrate temperature and substrate treatment. Ti3+ fractional composition are changed slightly between 0.11 and 0.17 and Ti4+ fractional compositio...