Zinc Oxide (ZnO) has great potential for applications on ultraviolet/blue light emitting devices because of high exciton binding energy and low cost. This research use low lattice-mismatched £^-LiAlO2 (LAO) substrate to grow ZnO epitaxial films by chemical vapor deposition (CVD). The first part of the present study deals with effect of processing parameters including temperature of Zinc procuser, sample position and growth temperature on ZnO epilayer. High the precuser temperature and long distance between sample and center of CVD furnace resulted in high growth rates. When growth rate was low, (10 0) ZnO (m-ZnO) was obtained and its crystallinity and luminescence property were poor. After increasing the growth rate to a certain extent, the surface of epilayer was flat and the crystallinity was improved. A further increase of growth rate resulted in a mixture of m-ZnO and c-plane in the ZnO epilayer. Based on the first part of study, the second part was focused on examining the effect of a nanosized buffer layer on inhibiting the nucleation of c-plane ZnO. Results showed that the nucleation of c-plane ZnO was indeed inhibited at low growth temperature. Finally, the crystallinity the optical property of the epilayer were improved by introducing a thick and flat buffer layer of ~170 nm in thickness.

Spin-polarized first-principles electronic structure and total energy calculations have been performed to better understand the magnetic properties of Co doped ZnO (ZnO:Co) with vacancies and Ga co-dopants. The paramagnetic state of ZnO:Co, in which Co ions lose their magnetic moments, has been found to be unstable. The total energy results show that acceptor-like Zn vacancies and donor-like Ga co-dopants render the anti-ferromagnetic (AFM) and ferromagnetic (FM) states to be more favorable, respectively. With O vacancies, ZnO:Co has been found to be in the weak FM state. These magnetic properties can be understood by the calculated O- and Zn-vacancies and Ga-co-dopant induced changes of the electronic structure, which suggest that AFM and FM Co-Co couplings are mediated by O 2p-Co majority (¡ô)-spin 3d hybridized states in the valence band of ZnO and O-vacancy-derived p states or Ga sp states in the ZnO band gap, respectively. For ZnO:Co with Zn vacancies (Ga co-dopants) the AFM (FM) coupling outweighs the FM (AFM) coupling and results in the AFM (FM) state, while for ZnO:Co with O vacancies, both the FM and AFM couplings are enhanced by similar degrees and result in the weak FM state. This study reveals a competition between FM and AFM couplings in ZnO:Co with vacancies and Ga co-dopants, the detailed balancing between which determines the magnetic properties of these materials.

This experiment use NaCl (001) single crystal as substrate, and the target is zinc oxide, to generate a-plane (112 ¡Â0) zinc oxide nanothim. The nanofilm is used as a buffer layer generating by Ion Beam Sputtering, and then increasing the thickness by Plasma sputtering. Part of specimens to proceed atmospheric heat treatment with different temperature and time, and part of specimens to change the ratio of the gas when the thin film is growth, then use of Transmission electron microscopy (TEM) and Photoluminescence (PL) as the analysis of film properties. The results of experiment, show that (112 ¡Â0) plane have more stringent conditions when generate of thin film, and easy to become the ring of electron diffraction with no-epitaxy .But finally we get a data what can generate a well a-plane ZnO thin film, the substrate temperature of 400 ¢X C, the sputtering time of 1 hour, Ar/O2 = 1.5. From the results of Photoluminescence, we find that there are zinc vacancies in ZnO thin film, probably there are too many oxygen atoms. While the heat treatment in nitrogen, zinc vacancies are reduced rapidly. Indicating that oxygen atoms within the film are reduced by nitrogen atoms or replace the position of the oxygen atoms.

In this study, we prepare the zinc oxide nanotip with aqueous solution deposited on ZnO nucleation layer. The thermal annealing with N2 ambiance at 300 oC for 1 hr increase the UV emission and decrease the defects. We use ZnO nanotip as an anti-reflection layer because of surface roughness and optical interference. ZnO nanotip with rough surface decreases reflection, so we use ZnO nanotip as an anti-reflection layer, after grown ZnO nanotip on solar cell the efficiency of solar cell was enhancement. The coordination modes were measured by Fourier-transform infrared spectrometer (FTIR). The physical properties were characterized by X-ray diffraction (XRD). The optical properties were measured by Micro-photoluminescence (Micro-PL). The morphology was observed by field emission scanning electron microscope (FE-SEM). The performance of the cells was measured by a semiconductor device analyzer. In our results, we grow the high performance of ZnO nanotip on solar cell to increase the efficiency. The short-circuit current increased from 42 to 51 mA, and the efficiency increased from 15.7 to 18.8 %.

The piezoelectric transducer for vibration-energy harvesting is constructed of a piezoelectric layer, bottom electrode and a top electrode. In order to obtain an appropriate transducer for the low-frequency operating; environmentally-friendly and long-term, the flexible substrate, the piezoelectric layer, and the additional mass-loading (tip mass) have been investigated thoroughly. This study investigates the feasibility of a high-performance ZnO and AlN based piezoelectric transducer for vibration-energy harvesting applications. Firstly, the piezoelectric transducer is constructed of a Cu/ZnO/ITO/PET structure. Both scanning electron microscopy and X-ray diffraction indicate that, among the favorable characteristic of the ZnO piezoelectric film include a rigid surface structure and a high c-axis preferred orientation. Hence, an open circuit voltage of 1.87 V for the ZnO piezoelectric transducer at a vibration frequency of 100 Hz is obtained by an oscilloscope. After rectifying and filtering, the output power of the generator exhibits an available benefit of 0.07 £gW/cm2 with the load resistance of 5 M£[. Secondly, this investigation introduces novel means of integrating high-performance piezoelectric transducers using single-sided ZnO and AlN films with a flexible stainless steel substrate (SUS304). Hence, the SUS304 substrate exhibits the long-term stability under vibration. The single-sided ZnO and AlN transducers are deposited on the SUS304 substrate at a temperature of 300 oC by an RF magnetron sputtering system. Scanning electron microscopy and X-ray diffraction of piezoelectric films reveal a rigid surface structure and a high c-axis-preferred orientation. A mass loading at the front-end of the cantilever is critical to increase the amplitude of vibration and the power generated by the piezoelectric transducer. The open circuit voltage of the single-sided ZnO power generator is 10.5 V. After rectification and filtering through a capacitor with a capacitance of 33 nF, the output power of the single-sided ZnO generators exhibited a specific power output of 1.0 £gW/cm2 with a load resistance of 5 M£[. Finally, this investigation fabricates double-sided piezoelectric transducers for harvesting vibration-power. The double-sided piezoelectric transducer is constructed by depositing piezoelectric thin films on both the front and the back sides of SUS304 substrate. The titanium (Ti) and platinum (Pt) layers were deposited using a dual-gun DC sputtering system between the piezoelectric thin film and the back side of the SUS304 substrate. Scanning electron microscopy and X-ray diffraction of piezoelectric films reveal a rigid surface structure and highly c-axis-preferring orientation. The maximum open circuit voltage of the double-sided ZnO power transducer is approximately 18 V. After rectification and filtering through a 33 nF capacitor, a specific power output of 1.3 £gW/cm2 is obtained from the double-sided ZnO transducer with a load resistance of 6 M£[. The variation of the power output of ¡Ó0.001% is obtained after 24-hour continuous test. The maximum open circuit voltage of the double-sided AlN power transducer is approximately 20 V. After rectification and filtering through a 33 nF capacitor, a specific power output of 1.462 £gW/cm2 is obtained from the double-sided AlN transducer with a load resistance of 7 M£[.

This thesis investigates the effects of varying the crystallographic orientations of epitaxial ZnO thin films to produce functional ZnO P-N diodes. First, with the atomic layer deposition (ALD), a p-type m-oriented ZnO epitaxial layer is deposited onto an also m-oriented Al2O3 substrate. Then an n-type ZnO layer, mostly textured along the c-axis, is grown atop to form a P-N diode by RF sputtering method. The Hall Effect of the m-ZnO thin film is measured separately at various temperatures and magnetic fields in Quantum Design¡¦s Physical Property Measurement System (PPMS) to determine the nature of the charge carriers. The m-oriented ZnO films are found to be p-type semiconductors, with carrier concentration approximately ~ 1021 1/cm3, which falls in the category of highly-doped degenerate semiconductor. In order to further prove that these films are indeed p-type, naturally n-type c-textured ZnO films are put on the m-films at room temperature by magnetron sputtering to see if the current-voltage (I-V) curves do follow the P-N junction characteristics. In optimizing the c-ZnO film quality and reducing the effects of the junction defects, the gas-mixture ratio between argon and oxygen was varied to compare for the changes in the performance of the resulted materials and devices. X-ray diffraction was used to characterize the crystallographic orientations and the general qualities of the samples by 2£c-£s scan, rocking scan, £p-scan and pole figure measurement. Understanding of the P-N diode is acquired through the analysis of the leakage current and the quantum tunneling phenomena as manifested in the I-V characteristics.

Due to the increased awareness of living and industrial safety, carbon monoxide detectors must be geared towards better portability and sensitivity. Metal oxide semiconductor sensors should possess advantages such as heat and corrosion resistance, low cost materials, and ease of miniaturization. This thesis applied ball milled and powdered ZnO and SnO2 to manufacture into paste, then used the screen printing method deposited ZnO and SnO2 paste film and silver electrode on glass substrate. The influence on sensing film materials, temperature, time of heat treatment, and temperature of measurement was investigated. The samples were fabricated and measured by setting up self-measurement apparatus. The data was analyzed the changes of resistance under different air and carbon monoxide environments. This is followed by analysis of both surface topography and microstructure of the sensing film under OM and SEM. Experiment reveals that samples under different annealing process yield different surface morphology and micro structure while at the beginning of the heat treatment, epoxy evaporates from the sample brought about porous structure. Annealing at higher temperature sample will have more rough surface and better sensitivity in detecting carbon monoxide. After epoxy removed, heat treatment mechanism is then switched to sinter ZnO and SnO2 powders. the longer the samples are sintered, the lower the sensitive. Sensing films composited with ZnO and SnO2 will have better carbon monoxide sensitivity at 300oC but its sensitivity decays at a faster rate than samples working at 250 oC despite the slightly weaker sensitivity. Sensing films with pure ZnO will have higher sensitivity compared to pure SnO2 one. With the increase of SnO2 proportion, carbon monoxide sensitivities of detectors decreases, however, its life time can be improve significantly.

In this study, the reactive rf magnetron sputtering was used to deposit zinc oxide (ZnO) thin films on Si substrate. The optimal sputtering parameters for film as luminescence application were found to be oxygen concentration (O2/O2+Ar) of 21%, RF power of 100W, substrate temperature of 500¢XC and sputtering pressure of 5 mtorr. Beside, the thermal treatment procedure was carried out to improve the luminescence characteristics of ZnO thin films. The physical characteristics of ZnO thin films deposited on Si substrate with different sputtering parameters were obtained by the analyses of XRD and SEM. The optical properties of ZnO thin films were discussed also. Ultraviolet (UV) visible spectrometer and photoluminescence spectrometer were used to measure the visible transmission and photoluminescence characteristics (PL), respectively. According to the experimental results, it is found that under optimal sputtering parameters, the emitted UV light intensity will be increased as the FWHM in x-ray diffraction is decreased, i.e. the grain size is larger. In addition, after post-deposition annealing at 800¢J, the strongest UV emission intensity was obtained in the nitrogen ambient and the strongest visible (green) emission intensity was obtained in the oxygen ambient.

In this study, the reactive rf magnetron sputtering was used to deposit zinc oxide (ZnO) thin films on SiO2/Si substrate at room temperature. The thermal treatment procedure was carried out to improve the luminescence characteristics of ZnO thin films. The physical characteristics of ZnO thin films with different post annealing process were obtained by the analyses of XRD and SEM. The electron spectroscopy for chemical analysis (ESCA) was used to analyze the chemical states of ZnO thin films. In optical properties, the photoluminescence spectrometer was used to measure the photoluminescence characteristics (PL). According to the results of experiments, the chemical states of ZnO thin films were changed after different post annealing. The photoluminescence characteristics were obtained at different wavelength, and the results indicated that they were affected by the chemical states of ZnO thin films. With 900¢J annealing, the strongest green emission and UV emission intensity can be obtained under the air ambient and the oxygen ambient, respectively. The reason was due to the variation of the proportion of oxygen vacancies and O-Zn bond within the ZnO thin films.

By integrating Nanotechnology and MEMS technology, this thesis aims to research a flexural-plate wave (FPW) sensor for testing Immunoglobulin E (IgE) concentration in blood serum, a significant index for the diagnosis of allergies. The traditional methods of blood assay are time-consuming and costly, and its average accuracy of only 60-70 percent. After compare the major four kinds of acoustic sensor, the FPW sensor demonstrates a high accuracy, high sensitivity, low operation frequency, low diagnosis time and low cost. This thesis utilizes a reactive RF sputter system to deposite the piezoelectric ZnO thin film. To obtain the high C-axis orientation (002) characteristic of ZnO membrane, many parameters such as substrate temperature, Ar/O2 ratio and RF power have been adjusted and optimized during the sputtering process. The effects of varied parameters will be investigated and analysis by using SEM or XRD facilities. In this study, we combined the high figure-of-merits ZnO deposition techniques and single-side anisotropic silicon etch process to implement the process integration of FPW device. Finally, this research has demonstrated a 50-60MHz center frequency can be extracted from such silicon-based FPW microsensor.