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Title: Structural and electrical properties of MnO films grown by pulsed laser deposition
Authors: Sin, Wai-lun
Keywords: Hong Kong Polytechnic University -- Dissertations
Manganese compounds
Pulsed laser deposition
Thin films -- Surfaces -- Magnetic properties
Thin films, Multilayered -- Magnetic properties
Issue Date: 2004
Publisher: The Hong Kong Polytechnic University
Abstract: Manganese monoxide (MnO) thin films of pure rock salt structure were prepared on single crystal MgO(001) and TiN buffered silicon(001) substrates by pulsed laser deposition method using dense ceramic Mn₃O₄ targets. In general, single phase MnO films were obtained at low ambient oxygen pressure of <10⁻⁴ Torr. Structural characterization by X-ray diffraction (XRD) showed that the MnO films started to crystallize at growth temperature as low as 200°C. Progressively improved crystalline structure and orientation were seen at higher deposition temperatures. XRD 360°-phi scans revealed epitaxial relationships of (001)MnO││(001)TiN││(00l)Si and (001)MnO││(00l)MgO for MnO films grown at low substrate temperature of 300 °C. MnO films of excellent structural quality were obtained at 600°C and under a base pressure of 2x10⁻⁵ Torr. In the case of MnO/TiN/Si, higher deposition temperature, however, caused structural deterioration in the MnO films due to chemical interdiffusion across the interface and oxidation of the TiN sub-layer. The electrical properties of the epitaxial MnO films integrated with Si were examined by depositing platinum spot electrodes to form a Pt/MnO/TiN/Si capacitor structure. MnO films grown at optimum condition yielded a room temperature dielectric constant of 17.4 with a dissipation factor as small as 0.049 at 10 MHz. They exhibited dielectric constant similar to that of bulk MnO single crystal. The correlation between leakage current and film thickness was also investigated. With an E-field of 1x10⁵ V cm⁻¹ applied across the MnO film, the leakage current decreased from 78.6 to 1.17x10⁻⁸ A cm⁻² for a film thickness change from 37 nm to 450 nm.
Resistivity versus temperature measurements revealed that the MnO films had a semiconducting transport behavior. Films deposited on MgO substrate exhibited a hopping energy of 0.51 eV and a thermal coefficient of resistivity that varied from -5.5 to -2.4 % K⁻¹ for different deposition pressure. Electrical measurements thus showed possible applications of MnO films as negative temperature coefficient (NTC) thermistor. Heteroepitaxial structures of Au/MnO/TiNIMgO(111) were also prepared. Electrical measurements on these heterostructures at temperature from 80 K to 310 K showed no obvious dielectric anomaly as those observed in bulk samples. This deviation was partially attributed to the stress and asymmetric interface nature of the thin film. Mixed-metal monoxides of composition of MnxCo₁-xO were fabricated too. Structural and electrical conduction of epitaxial films with 0<x<1 were studied. The lattice parameters of these films were tuned from 0.426 nm to 0.441 nm according to Vegard's law based on the mole ratio (x). The structural measurement showed possible applications as template for strain layer growth.
Description: xviii, 136 leaves : ill. ; 30 cm.
PolyU Library Call No.: [THS] LG51 .H577M AP 2004 Sin
Rights: All rights reserved.
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