Chun Keun Kim

Characterization of the oxidized indium thin films with thermal oxidation

Abstract Oxidized indium thin films on several substrates were formed by indium deposition and thermal oxidation. The oxidation was carried out in oxygen ambient at temperatures ranging from 500 to 900°C for 1 h. In the scanning electron microscopy measurements, the oxidized indium films were shown to be composed of grains with sizes of 400 to 600 nm which agglomerate subgrains with diameters of 40–60 nm. From the measurements of X-ray diffraction, X-ray photoelectron spectroscopy and Auger electron spectroscopy, it was confirmed that the oxidized indium are cubic indium oxide (In 2 O 3 ) polycrystallites. In addition, no elements other than In and O atoms were found from secondary ion mass spectroscopy measurements. A strong orange photoluminescence, peaking at 637 nm, was observed at room temperature for these films. It was assumed that a center of orange luminescence in the indium oxide films may be related to oxygen deficiencies or defects.

Visible luminescences from thermally grown silicon dioxide thin films

We introduce visible photoluminescences (PL) of violet (432 nm) and yellow (561 nm) at room temperature from thermally treated silicon dioxide thin films. These luminescences were very strong with a near infinite degradation time. At an oxide layer thickness less than 200 nm, these luminescences were not seen, even with high temperature annealing at about 1000 °C. As a result of photoluminescence, x‐ray photoelectron spectroscopy, Fourier transform infrared, and high‐resolution transmission electron microscopy measurements, we conclude that the violet PL originates from the nanocrystalline silicon formed in the silicon oxide film by the thermal strain effect between the silicon substrate and the silicon dioxide film, while the yellow PL originates from the radiative decay of self‐trapped excitons that are confined to oxygen sufficient structures.

Carbon doping characteristics of GaAs and Al0.3Ga0.7As grown by atmospheric pressure metalorganic chemical vapor deposition using CCl4

Abstract This paper presents the results of a Van der Pauw-Hall analysis of the carbon doping characteristics of GaAs and Al 0.3 Ga 0.7 As epilayers grown by atmospheric pressure metalorganic chemical vapor deposition (AP-MOCVD) using carbon tetrachloride (CCI 4 ). It also describes the effects of rapid thermal annealing (RTA) on the electrical properties of CCI 4 -doped GaAs. Heavily CCI 4 -doped GaAs and Al 0.3 Ga 0.7 As epilayers with a wide range of hole concentrations were obtained by varying the growth temperature from 500 to 750°C and by varying the V/III (AsH 3 /TMG) ratio from 5 to 20 while keeping the flow rate of CCI 4 constant. CCI 4 -doped GaAs epilayers with hole concentrations between 3.5 × 10 17 and 8.95 × 10 19 cm -3 were obtained under the above growth conditions with constant TMG flow rate. CCI 4 -doped Al 0.3 Ga 0.7 As epilayers have higher hole concentrations than CCI 4 -doped GaAs epilayers for various growth temperatures at the same V/III ratio and CCI 4 flow rate, and the hole concentration increases with decreasing growth temperature. The CCI 4 -doped GaAs epilayers have nearly the same Hall mobilities as GaAs C-doped by V/III ratio control, but higher mobilities than Zn-doped GaAs. Our results show that the free hole concentration is heavily CCI 4 -doped GaAs epilayers increases after RTA at 790°C. This can be attributed to the decrease in the concentration of the hydrogen atoms caused by the breaking of the C-H or C-H x bonds. After longer annealing at 790°C the hole concentration decreases and the hole mobility increases. It is suggested by the increase in free hole concentration by RTA that the activation efficiency of the incorporated carbon in the as-grown CCI 4 -doped GaAs epilayers is incomplete.

The roles of ruthenium nanoparticles decorated on thin multi-walled carbon nanotubes in the enhancement of field emission properties

The roles of metal nanoparticles (NPs) decorated on carbon nanotubes (CNTs) in the enhancement of field emission properties were investigated by measuring the work functions (WF), densities of state (DOS), turn-on fields, current densities, and sizes of NPs. RuO2 was deposited on CNTs and reduced to Ru by annealing at elevated temperatures. The WF decreased during reduction, and integrated DOS increased after the formation of Ru NPs. Consequently, the turn-on field showed strong correlation with the WF, and the shape of the Ru NPs had a more significant impact on current density than the WF and DOS.

InGaAs layer effect on the growth of AlGaAs/GaAs quantum wires on V-grooved InGaAs/GaAs substrates

Abstract An effect of InGaAs layer on the growth of AlGaAs GaAs quantum wires (QWRs) on V-grooved InGaAs GaAs (1 0 0) substrates has been studied. The structures are grown by atmospheric pressure metalorganic chemical deposition (MOCVD) and characterized with scanning electron microscope, transmission electron microscope and photoluminescence (PL) measurements. The thick InGaAs layer causes to form several facets in the side walls of V-grooves. Especially, the side walls near the bottom are convexly shaped, resulting in narrowing the width near the bottom of V-groove. QWRs grown on this substrate show a blue shift in the PL spectra, while any PL signal from the top-QWLs on InGaAs layer is not obtained. These results may be originated from the narrowing effect of the InGaAs layer on the bottom and from the poor crystallinity of the top epilayer on the InGaAs layer with many dislocations.