S. S. Yom

Structural properties of BaTiO3 thin films on Si grown by metalorganic chemical vapor deposition

Ferroelectric BaTiO3 thin films were grown on Si(100) substrates at a temperature of 600 °C by in situ metalorganic chemical vapor deposition. X‐ray diffraction and transmission electron microscopy results suggested that the 〈110〉 direction of the BaTiO3 preferred oriented films is parallel with the (100) direction of the Si substrates. Auger electron spectroscopy measurements showed that the compositions of the as‐grown films were with a uniform distribution throughout the thickness of the films and with a sharp interface. These results indicate that the failure to obtain BaTiO3 epitaxial films was due to the formation of an interfacial amorphous layer prior to the creation of the films.

Growth of γ-Al2O3 thin films on silicon by low pressure metal-organic chemical vapour deposition

Abstract Metal-organic chemical vapour deposition of Al2O3 using aluminium isopropoxide (Al(OC3H7)3) and nitrous oxide (N2O) via thermal pyrolysis was investigated with the goal of producing high quality Al2O3p-Si(100) interfaces. From the X-ray diffraction analysis, the film was found to be a γ-Al2O3 heteroepitaxial film. The stoichiometry of the grown Al2O3 film was similar to that of sapphire observed from Auger electron spectroscopy. Room temperature capacitance-voltage measurements clearly reveal metal-insulator-semiconductor behaviour for samples with the Al2O3 insulator gate, and the interface state densities at the Al2O3p-Si heterointerface were approximately 1011 eV−1 cm−2, at levels centred in the silicon energy gap.

POSTGROWTH ANNEALING EFFECTS OF TIO2 THIN FILMS GROWN ON INP SUBSTRATE AT LOW-TEMPERATURE BY METAL-ORGANIC CHEMICAL-VAPOR DEPOSITION

The structural and electrical properties of titanium dioxide (TiO2) thin films grown on n‐type InP(100) substrate by low‐pressure metal‐organic chemical‐vapor deposition have been studied with postannealing. The thin films of TiO2 were deposited at a low temperature of 350 °C using titanium isopropoxide and oxygen. After a postgrowth annealing by the rapid thermal annealing method at a temperature of 850 °C for 15 s, the TiO2/InP structure of only the anatase phase with (101) and (200) peaks was observed by x‐ray diffraction analysis. No interface reaction between TiO2 and InP was detected by Auger electron spectroscopy depth profiling. From capacitance–voltage measurement of the Al/TiO2/n‐InP structure, the interface density of states at midgap energy and the dielectric constant were approximately low 1012 eV−1 cm−2 at midgap energy and about 50, respectively.

Structural and electrical properties of BaTiO3 thin films grown on p‐InSb substrate by metalorganic chemical vapor deposition at low temperature

Metalorganic chemical vapor deposition of BaTiO3 on p‐InSb (111) using Ba(tmhd)2, Ti(OC3H7)4, and N2O via pyrolysis at low (∼300 °C) temperature was performed to produce high‐quality BaTiO3/p‐InSb (111) interfaces and BaTiO3 insulator gates with dielectric constants of high magnitude. Raman spectroscopy showed the optical phonon modes of a BaTiO3 thin film. The stoichiometry of the BaTiO3 film was investigated by Auger electron spectroscopy. Transmission electron microscopy showed that the BaTiO3 films had local epitaxial formations. Room‐temperature capacitance‐voltage measurements clearly revealed metal‐insulator‐semiconductor behavior for the samples with the BaTiO3 insulator gates, and the interface state densities at the BaTiO3/p‐InSb interfaces were approximately high 1011 eV−1 cm−2 at the middle of the InSb energy gap. The dielectric constant determined from the capacitance‐voltage measurements was as large as 743. These results indicate that the BaTiO3 layers grown at low temperature can be used f...

Structural properties of titanium dioxide films grown on p-Si by metal-organic chemical vapor deposition at low temperature

Abstract Metal-organic chemical vapor deposition of TiO 2 via pyrolysis using Ti (OC 3 H 7 ) 4 and N 2 O was investigated with the goal of producing TiO 2 epitaxial films on p-Si(100) substrates. X-ray diffraction analysis showed that the grown TiO 2 layer was a polycrystalline film. Auger depth profiles demonstrated that the TiO 2 /Si interface was relatively abrupt, and transmission electron microscopy verified the formation of an interfacial layer in the TiO 2 /Si interface and the formation of a polycrystalline TiO 2 thin film. These results indicate that the failure to form the TiO 2 epitaxial films originated from the formation of an interfacial amorphous layer at the initial growth stage.

Structural and electrical properties of Al2O3 thin films on p-Si grown by low-pressure metalorganic chemical vapor deposition

Abstract Al2O3 films were grown by metalorganic chemical vapor deposition on p-Si(100) orientation substrates using Al(OC3H7)3 and N2O via pyrolysis. Raman spectroscopy showed the optical phonon modes of the Al2O3/Si structure. The stoichiometry of the Al2O3 film was observed by Auger electron spectroscopy. Capacitance-voltage measurements clearly showed metal-insulator-semiconductor behaviors for the Al/Al2O3/Si diodes with the Al2O3 insulator gate, and the interface state densities at the Al2O3/Si interface were approximately 1011 eV cm-2 at the middle of the Si energy gap. These results indicate that Al2O3 films on Si have potential applications as insulator films.

The interfacial layer formation of the Al2O3/Si structures grown by low‐pressure metalorganic chemical vapor deposition

Metalorganic chemical vapor deposition of Al2O3 using Al(O‐C3H7)3 and N2O via pyrolysis was investigated with the goal of producing Al2O3 epitaxial films on p‐Si (100) substrates. Room‐temperature capacitance‐voltage measurements clearly showed metal‐insulator‐semiconductor behaviors for the samples with the Al2O3 insulator gate, and the interface state densities at the Al2O3/p‐Si interface were approximately 1011 eV−1 cm−2 at the middle of the Si energy gap. Auger depth profiles demonstrated that the Al2O3/Si interface was not abrupt, and transmission electron microscopy verified the formation of an interfacial layer in the Al2O3/Si interface and the formation of a polycrystalline Al2O3 thin film. These results indicated that the failure to form Al2O3 epitaxial films was due to the formation of an interfacial layer prior to the growth of the Al2O3 layer.

Infrared properties of single crystal MgAl2O4, a substrate for high-temperature superconducting films

Abstract Infrared optical characterization of single crystal SrTiO 3 , an important substrate for high-T c superconducting films, had been studied by transmission and reflection measurements. We measured absorption spectrum of this crystal, from 50 – 5000cm −1 and 80 – 300 K. This crystal has highly reflectivity behavior in far-infrared (FIR) range. The vibration modes of this crystal are clearly shown temperature dependent behavior. The main absorption dips of FIR reflection measurements are shown in 170, 483 cm −1 at 80 K. These dips have 3 cm −1 shift at temperature from 300 K down to 80 K. In addition to this main dips, there is another dip appeared at 441cm −1 when the temperature down below 100 K. This feature did not show in previous reports. The vibration modes of this crystal substrate, as well as dielectric behaviors that are important characteri for analyzing superconducting films will go further studies.

Magnetotransport and electron subband studies of edge delta‐doped Al0.27Ga0.73As/GaAs single quantum wells

Shubnikov–de Haas and Van der Pauw Hall effect measurements at 1.5 K have been carried out to investigate the existence of a two‐dimensional electron gas and to determine subband energies in a Si‐delta‐doped Al0.27Ga0.73As/GaAs single quantum well. The fast Fourier transformation results for the S‐dH data indicate clearly the occupation of two subbands in edge delta‐doped Al0.27Ga0.73As/GaAs quantum wells. Capacitance‐voltage profiling and temperature‐dependent photoluminescence measurements have been performed to characterize the properties of edge delta‐doped Al0.27Ga0.73As/GaAs quantum wells. Using these experimental results and a self‐consistent numerical method which took into account the exchange‐correlation effects, the electron subband energies were determined. These results indicate that edge delta‐doped Al0.27Ga0.73As/GaAs single quantum wells are similar to the asymmetrical potential wells occupied by relatively high electron carrier densities.

Formation of circular-shaped crystalline phases embedded in amorphous PbTiO3 thin films grown by MOCVD

Abstract We deposited PbTiO3 thin films using β-diketonate complex of Pb(tmhd)2 and titanium-isopropoxide as source precursors at substrate temperature range from 430 °C to 630 °C by MOCVD. The PbTiO3 films on Pt/Ti/SiO2/Si substrates at above 500 °C showed polycrystalline behavior. The PbTiO3 films on Pt/Ti/SiO2/Si and hsed silica glass substrates grown at 430 °C included abnormal circular-shaped crystalline phases which were randomly embedded in amorphous PbTiO3 film. From Auger electron spectroscopy, transmission electron microscopy and micro-Raman spectroscopy results, the circular-shaped phase is an aggregation of micro-crystalline PbTiO3 phases which are embedded in the amorphous matrix.