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Al-doped ZnO films were grown on quartz substrates by MOCVD. A systematical and detailed study about the effect of Al content on structural, optical and electrical properties were discussed. XRD measurements revealed that the preferred orientation of ZnO films decreased with the increase of Al content. AFM images indicated that the TMA molecules or their decomposition products bringing down the surface activity of ZnO grains, and so grain growth is inhibited. By the band tail states and the quantum confinement effect, the UV emission peak initially red-shifted and then blue-shifted. All Al-doped samples demonstrated more than 80% of the optical transparency in the visible region. Low electrical resistivity of Al-doped ZnO films was obtained. However, due to defects and grain boundary scattering which caused by Al doping, the hall mobility is increased initially and then decreased.

Highly preferred orientation 3C-SiC films were deposited on Si (111) substrates by a modified two-step carbonization method. The crystal quality of SiC films were examined by XRD. To evaluate the effect of the introducing of silane during carbonization, cross-sectional SEM was carried out. Results indicated that the introducing of silane during carbonization is effective to prevent the out-diffusion of silicon atoms from silicon substrates. And by adjusting the carbonization conditions, void-free 3C-SiC films were obtained. XPS results demonstrated that the prepared 3C-SiC films were corresponding with the stoichiometric ratio.

The properties of ZnO films grown on Si (1 1 1) substrates by Metal-Organic Chemical Vapor Deposition technique using diethylzinc and H 2 O as reactant gases are reported. The primary focus is on understanding the origin of deep-level luminescence. As increasing the annealing temperature, a visible emission is observed both in samples annealing in oxygen atmosphere and nitrogen atmosphere. In addition, this broad defect emission becomes obviously asymmetric when the annealing temperature was increased to 1000 °C in oxygen atmosphere. Theoretical investigations have reported that the formation enthalpy of defects is varied under different conditions. With these results, it is suggested that the visible emission in ZnO films annealed in oxygen atmosphere is related to zinc vacancy and oxygen interstitial defects. While, the green emission in ZnO films which were annealed in nitrogen atmosphere is attributed to oxygen vacancy defects.

Hetero-junctions have been fabricated on Al-doped silicon carbide thin films onto n-type silicon single crystals using low-pressure chemical vapor deposition method. Temperature-dependent current–voltage measurements and Hall-effect measurements have been performed to determine the electrical properties of the structures. The temperature-dependent I–V characteristics demonstrated that the forward conduction at lower voltages was dominated by thermionic emission process, while, the forward conduction at higher voltages was determined by multi-step tunneling current. The activation energy of saturation current was about 0.32 eV. Hall-effect measurements proved the p-type properties of obtained SiC films. Deduced from the results of Hall measurements, the junction built-in potential was 1.32 V at room temperature. Moreover, using deep level transient spectroscopy measurements, AlSi acceptor ionization energy was estimated.

The D°h luminescence of ZnO films deposited on p-type Si substrates is produced by metal-organic chem-ical vapor deposition (MOCVD). After annealing in the air at 700°C for an hour, the photoluminescence (PL) spectra, the {itI-V} characteristics and the deep level transient spectro-scopy (DLTS) of the samples are measured. All the samples have a rectification characteristic. DLTS signals show two deep levels of {itE}{in1} and {itE}{in2}. The Gaussian fit curves of the PL spectra at room temperature show three luminescence lines {itb}, {itc} and {itd}, of which {itb} is attributed to the exciton emission. The donor level {itE}{in1} measured by DLTS and the location state donor ionization energy {itE}{ind} of the closely neighboring emission lines {itc} and {itd} are correlated. {itE}{in1} is judged as neutral donor bound to hole emission (D°h). Moreover, the intensity of the PL spectra decreases while the relative density of {itE}{in2} increases, showing that {itE}{in2} has the property of a non-radiative center.

A series of heterojunctions consisting of intrinsic zinc oxide (ZnO) films and p-type Si substrates have been prepared by DC reactive sputtering. The ZnO films were grown at different conditions, and the influence of growth conditions on photovoltaic (PV) property was discussed. It was found that both growth temperature and oxygen partial pressure play important roles for enhancing the PV effect of the samples. By optimizing growth conditions, the PV efficiency has been improved and also by more magnitudes. The open circuit voltage (Voc) and short circuit current (Isc) per square centimeter arrived at 350 mV and 2.5 mA, respectively. The variation mechanism of PV effect with growth conditions has been investigated in order to understand the photoelectric conversion behavior of the ZnO/Si heterojunction.

P-type ZnO film was obtained by N-implantation at energy of 120 keV with annealing at 850 °C in oxygen. Room temperature Hall effect measurements revealed that the carrier concentration and mobility was 9.95 × 10 18 cm −3 and 14.3 cm 2 /vs, respectively, in the implanted ZnO with optimal fluence of 10 15 N/cm 2 , where more N acceptors were activated as confirmed by X-ray diffraction and photoluminescence. The increase of lattice constants and appearance of emission peaks at 3.26 and 3.18 eV after implantation indicated that the p-type ZnO was realized by substitution of N atom for O sublattice.

Cubic SiC (3C-SiC) film has been deposited on Si (1 1 0) substrate by the low pressure chemical vapor deposition (LPCVD) with gas sources of SiH4, C3H8 and carrier gas of H2. The 3C-SiC crystalline film can be confirmed through the observations using reflection high-energy electron diffraction (RHEED) images. The X-ray diffraction (XRD) pattern and the rocking curve indicate that the (1 1 1) plane of SiC film is parallel to the surface of the Si (1 1 0) substrate and the film is of high crystallinity. The results of the field emission scanning electron microscope (FESEM) images show that the film has smooth surface morphology. Transmitted electron diffraction (TED) pattern and high resolution transmission electron microscope (HRTEM) image further confirm the high quality of the film.

ZnO films have been grown on Si(111) substrates by metal-organic chemical vapor deposition using diethylzinc and CO2 as precursors. The effects of growth temperature on growth rate, structure, and optical properties of the ZnO films were investigated in a temperature range between 450 and 700°C. As growth temperature increased, the growth mode changed from kinetics-limited to mass-transfer-limited, and finally, to desorption-limited mode. Using the Arrhenius equation, the activation energy for the kinetics-limited growth mode was estimated to be 105meV. The crystalline quality was also strongly dependent on growth temperature. With increasing growth temperature, the width of x-ray diffraction peaks decreases and the photoluminescence intensity enhances. Using CO2 as the oxygen source, we found that the optimal growth temperature was near 600°C.

ZnO films with strong c-axis-preferred orientation have been prepared by a single source chemical vapor deposition technique using zinc acetate as source material at the growth temperature of 230 °C. The strong UV and blue emissions were observed in the photoluminescence spectra of as-grown films. A small quantity of residual zinc acetate was reserved on the surface of as-grown ZnO films and the emission mechanism of blue luminescence was nearly related to the CH3COO– of unidentate type. The blue emission disappeared and the green emission appeared after annealing treatment. The green emission is related to the singly ionized oxygen vacancies.

ZnO films have been grown by a sol–gel process on Si (1 1 1) substrates with and without SiC buffer layers. The influence of SiC buffer layer on the optical properties of ZnO films grown on Si (1 1 1) substrates was investigated. The intensity of the E 2 (high) phonon peak in the micro-Raman spectrum of ZnO film with the SiC buffer layer is stronger than that of the sample without the SiC buffer layer, and the breadth of E 2 (high) phonon peak of ZnO film with the SiC buffer layer is narrower than that of the sample without the SiC buffer layer. These results indicated that the crystalline quality of the sample with the SiC buffer layer is better than that of the sample without the SiC buffer layer. In photoluminescence spectra, the intensity of free exciton emission from ZnO films with the SiC buffer was much stronger than that from ZnO film without the SiC buffer layer, while the intensity of deep level emission from sample with the SiC buffer layer was about half of that of sample without the SiC buffer layer. The results indicate the SiC buffer layer improves optical qualities of ZnO films on Si (1 1 1) substrates.

ZnO films have been grown on Si(1 1 1) substrates by metal-organic chemical vapor deposition. The Si substrates were pretreated by the Ar + plasma bombardment before the ZnO growth for the purpose of eliminating the remnant amorphous silica layers from the substrates’ surface. The effects of the plasma pretreatment on the growth of ZnO were investigated. The crystalline quality, surface morphology and photoluminescence property of the ZnO films were significantly improved by the pretreatment process. However, with increasing the plasma power, the quality of ZnO films was degraded due to the damage of the Si substrates by the bombardment.

SiC films have been deposited on C-plane (0 0 0 1) sapphire substrates by low pressure chemical vapor deposition (LPCVD). The 3C-SiC and 6H-SiC polytype kinds of the films grown at two different growth parameters (growth temperature and flow rate of silane) were verified by Raman spectra analysis. The results of XRD patterns and rocking curves show the films are of good crystalline quality. The microstructure of the films was measured by high resolution transmission electron microscopy (HRTEM). Field emission scanning electron microscope (FESEM) and atomic force microscope (AFM) were used to evaluate the surface morphology. The chemical bond and composition of the films were characterized by X-ray photoelectron spectra (XPS). All of these results further confirm that the SiC films are of good quality.

Zinc oxide (ZnO) thin films were grown on Si (1 0 0) substrates by pulsed laser deposition (PLD) using two-step epitaxial growth method. Low temperature buffer layer (LTBL) was initially deposited in order to obtain high quality ZnO thin film; the as-deposited films were then annealed in air at 700 °C. The effects of LTBL and annealing treatment on the structural and luminescent properties of ZnO thin film were investigated. It was found that tensile strain was remarkably relaxed by employing LTBL and the band-gap redshifted, correspondingly. The shift value was larger than that calculated from band-gap theories. After annealing treatment, it was found that the annealing temperature with 700 °C has little influence on strains of ZnO films with LTBLs other than directly deposited film in our experiments. Interestingly, the different behaviors in terms of the shift of ultraviolet (UV) emission after annealing between films with and without buffer were observed, and a tentative explanation was given in this paper.

ZnO films were grown on Si (100) substrates at low pressure in a vertical metal-organic chemical vapor deposition reactor with different total gas velocity. The structure and photoluminescence property of the undoped ZnO films grown with different flow rates of N 2 eluting gas were investigated. The structure quality was improved as the N 2 flow rate increased. In addition, when the flow rate of N 2 eluting gas was higher than 1.4 slm, a new luminescence peak which was attributed to the N-related defect was detected at room temperature, besides the other two peaks near the band gap, which were due to radiation of the free exciton and the electron from the donor level to the valence band respectively, also appeared at low flow rate of N 2 eluting gas.

Nanocrystalline ZnO thin films on p-type Si(1 0 0) substrates have been prepared by a sol-gel method. X-ray diffraction results showed polycrystalline wurtzite with a preferential (0 0 2) orientation. Morphology studies revealed that the films consisted of uniform grains in size of ∼33 nm. A strong ultraviolet emission with no distinct visible emissions was observed in room temperature photoluminescence spectrum. The ultraviolet emission results from the recombination of free exciton with stronger longitudinal optical (LO) phonon replica. Stronger LO phonon replica may be ascribed to the strong interaction between the exciton and LO phonon in nanostructure. Nanostructure of films is also responsible for the blueshift of free exciton emission compared with single-crystal ZnO. The absence of E 1 (LO) mode in Raman spectrum further confirmed low defect density in as-grown nanocrystalline ZnO films. The electrical junction properties characterized by current–voltage measurement showed a rectifying behavior.

Nanocrystalline zinc oxide (nc-ZnO) films were prepared by a sol–gel process on p-type single-crystalline Si substrates to fabricate nc - ZnO/p-Si heterojunctions. The structure and morphology of ZnO films on Si substrates, which were analyzed by X-ray diffraction (XRD) spectroscopy and atomic force microscopy (AFM), showed that ZnO films consisted of 50–100 nm polycrystalline nanograins with hexagonal wurtzite structure. The electrical transport properties of the nc-ZnO/p-Si heterojunctions were investigated by temperature-dependent current–voltage ( I–V ) measurements and room temperature capacitance–voltage measurements. The temperature-dependent I–V characteristics revealed that the forward conduction was determined by multi-step tunneling current, and the activation energy of saturation current was about 0.26 eV. The 1/ C 2 – V plots indicated the junction was abrupt and the junction built-in potential was 1.49 V at room temperature.

Potassium titanate nanowires have been synthesized by a hydrothermal method using anatase and brookite nanocrystallites, respectively, as precursors. The corresponding products, alpha- and beta-K 2 Ti 6 O 13 nanowires, have distinct differences in structure and properties. Under the same conditions, the amount of K intercalated into anatase TiO 2 is larger than that into brookite TiO 2 . The multiple types of reserved short Ti–O bonds in beta-K 2 Ti 6 O 13 confined the growth of nanowires along the [010] orientation and made the beta-K 2 Ti 6 O 13 nanowires stubby. The UV–vis absorption spectrum of beta-K 2 Ti 6 O 13 nanowires showed strong and wide absorption in the ultraviolet and visible region. Beta-K 2 Ti 6 O 13 is thermodynamically more stable than alpha-K 2 Ti 6 O 13 .

Silver (Ag) doped and undoped ZnO films were grown on Si (100) substrates by the sol-gel process. Photoluminescence (PL) of two kinds of samples as a function of the excitation intensity has been measured, and PL intensities have been fitted by a power law. It is found that Ag doping increases the intensity of free emission from ZnO and does not change the position and the full width at half-maximum of the free exciton emission. In PL spectra of two kinds of samples under various excitation powers, no visible emission bands related to the deep levels were observed. These results reveal that doped Ag in ZnO films only enhances emission efficiency from free exciton recombination, not giving rise to new emissions.

Highly orientated ZnO thin films and the self-organized ZnO nanorods can be easily prepared by a simple chemical vapor deposition method using zinc acetate as a source material at the growth temperature of 180 and 320 °C, respectively. The ZnO thin films deposited on Si (100) substrate have good crystallite quality with the thickness of 490 nm after annealing in oxygen at 800 °C. The ZnO nanorods grown along the [0001] direction have average diameter of 40 nm with length up to 700 nm. The growth mechanism for ZnO nanorods can be explained by a vapor–solid (VS) mechanism. Photoluminescence (PL) properties of ZnO thin films and self-organized nanorods were investigated. The luminescence mechanism for green band emission was attributed to oxygen vacancies and the surface states related to oxygen vacancy played a significant role in PL spectra of ZnO nanorods.

The surface topographies of as-sputtered and annealed ZnO films were measured by atomic force microscope (AFM). Multifractal behavior of AFM images has been analyzed by box-counting method. It is found that the scaling range can be extended from the image size to the smallest pixel (about 3 decades) by selecting an appropriate method for determining height probability and neglecting smallest probabilities (totally

The emission properties of ZnO films deposited on Si substrates by reactive dc sputtering have been studied using synchrotron radiation (SR). The integrated luminescence spectra as well as the spectra at a fast time window from about 4 ns to 8 ns and a slow time window from about 20 ns to 160 ns were measured simultaneously, at a temperature range from several K to 300 K. Apart from the bound-exciton radiation recombination (peaked at 369.5 nm) and ultraviolet emission band (peaked at 380 nm), a new emission band peaked at 290 nm was found for the first time under SR vacuum ultraviolet excitation. The mechanisms of these photoluminescence emissions are discussed.

Fractal image processing has been applied to characterize the surface roughness of ZnO films as measured by atomic force microscopy. The simple fractal analysis suggests that the fractal dimension D can be used to describe the change of the whole grain morphology along the growth direction. Multifractal analysis shows that the scaling range is close to three orders of magnitude, which is larger than that of a simple fractal and most empirical fractals. The width of the multifractal spectrum can be used to characterize the roughness of the film surface quantitatively and the shape of multifractal spectrum can describe the ratio between the number of the lowest valleys and the highest peaks statistically.

The structure and photoluminescence (PL) at room temperature of ZnO films deposited on Si(111) substrates by metal-organic chemical vapor deposition (MO-CVD) using diethylzinc (DEZ) and CO 2 was investigated. It was found that these properties strongly depend on growth temperature and pressure. ZnO films can be deposited only at low pressure and in the temperature region of 500–650°C. The samples grown at certain conditions can generate stronger luminescence of ZnO. When the growth temperature increased to 650°C, the ZnO 2 phase was observed in X-ray diffraction (XRD) patterns of the samples. This characteristic became evident after the samples annealed. Appearance of a ZnO 2 phase results in production of a new emission band centered at 575 nm in the PL spectrum at room temperature, and the green emitting band also disappears.

A series of ZnO films with TiO 2 buffer on Si (1 0 0) substrates were prepared by DC reactive sputtering. Growth temperature of TiO 2 buffer changed from 100 °C to 400 °C, and the influence on the crystal structures and optical properties of ZnO films have been investigated. The XRD results show that the ZnO films with TiO 2 buffer have a hexagonal wurtzite structure with random orientation, and with the increase of growth temperature of TiO 2 buffer, the residual stresses were released gradually. Specially, the UV emission enhanced distinctly and FWHMs (full width half maximum) decreased linearly with the increasing TiO 2 growth temperature. The results all come from the improvement of crystal quality of ZnO films.

ZnO films were prepared on p-Si (100) substrates by direct current (DC) sputtering with and without TiO 2 buffer. The crystal structures, surface morphologies and optical properties were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescence (PL). XRD results indicated that the growth mode of ZnO film was changed from strong (002) preferential orientation to several crystal orientations by introducing TiO 2 buffer, and the residual strain was reduced. SEM manifested that ZnO film with TiO 2 buffer had the uniform grain size and flat surface. In addition, stronger ultraviolet emission was observed from ZnO film with TiO 2 than that without at room temperature. The low temperature photoluminescence was investigated to understand the different PL mechanism of ZnO films.

Ag–S codoped ZnO thin films have been fabricated on Si substrates by radio frequency (RF) magnetron sputtering using a thermal oxidation method. XRD and SEM measurements showed that the sample has hexagonal wurtzite structure with a preferential (002) orientation and the surface is composed of compact and uniform grains. AgZn–nSO defect complexes were observed in the Ag–S codoped ZnO films by XPS analysis. Low temperature PL spectra showed neutral acceptor bound exciton emission related to AgZn–nSO. The corresponding acceptor ionization energy of 150 meV is much lower than that of monodoped Ag (246 meV), which is favorable for p-type doping of ZnO.

Cathodoluminescence and photoluminescence properties of ZnO films deposited on Si substrates are presented. The electronic states of the ZnO film are assigned by means of the reflection spectra and photoelectron spectra in UV–VUV region. The luminescence spectrum consists of two main emission bands peaking at 392 nm (UV) and 523 nm (green). Intensity of the UV band superlinearly increases with rising density of the electron beam, while intensity of the green band increases sublinearly.

Silver-doped ZnO films were grown on glass substrates by RF reactive magnetron sputtering. The as-grown ZnO:Ag film is insulating but behaves as p-type conduction with a resistivity of 152 Ω cm, a carrier concentration of 2.24×10 16 cm −3 and a Hall mobility of 1.83 cm 2 /V s after annealing in O 2 atmosphere at 600 ∘ C for 1 h. The influence of post-annealing temperature and ambience on the electrical, structural and optical properties of the films was investigated.

Cubic SiC (3C-SiC) films were deposited on on-axis 6H-SiC (0001) substrates by low-pressure chemical vapor deposition (LPCVD). The result of X-ray diffraction patterns shows that the 3C-SiC films were of good crystalline quality. The influence of the growth parameters (flow rates of the gas sources and growth temperature) on the growth rate of the SiC films is discussed. The results show that the transport of silane or its reaction products is the limiting factor for the growth. The surface morphology of the SiC films was observed by atomic force microscope imaging. From these results it can be concluded that the growth of the films is in agreement with a Stranski-Krastanov growth mode.

The highly c-axis oriented ZnO films were deposited on Si substrates with Zn buffer layers. The intense cathodoluminescence, including UV, blue, and green emissions, was observed in these films at room temperature. According to X-ray diffraction analysis and cathodoluminescence spectra, it is found that the Zn buffer layer plays an important role for improving crystal quality of films and for getting intense cathodoluminescence.

The photoluminescence (PL) spectra of the undoped ZnO films deposited on Si substrates by dc reactive sputtering have been studied. There are two emission peaks, centered at 3.18 eV (UV) and 2.38 eV (green). The variation of these peak intensities and that of the I–V properties of the ZnO/Si heterojunctions were investigated at different annealing temperatures and atmospheres. The defect levels in ZnO films were also calculated using the method of full-potential linear muffin-tin orbital. It is concluded that the green emission corresponds to the local level composed by oxide antisite defect OZn rather than oxygen vacancy VO, zinc vacancy VZn, interstitial zinc Zni, and interstitial oxygen Oi.

A-axis preferred orientation AlN thin films are deposited on Si(100) substrates by radiofrequency-assisted metal organic chemical vapor deposition method. Use high-purity nitrogen as nitrogen precursor and trimethyl-aluminum as aluminum precursor, respectively. Crystalline quality, surface morphology and other properties of the films are investigated by X-ray diffraction and scanning electron microscope method. The results show that a higher growth temperature is helpful for improving the quality of AlN films, while increasing of nitrogen carrier gas flow rate and the radiofrequency power within a certain range will be conducive to the growth of AlN films, but excessively high flow rate or radiofrequency power will be adverse for the growth of AlN films.

A type of semiconductor heterostructure fabricated by zinc-oxide films deposited on silicon substrates is investigated. The current-voltage characteristics under dark or illumination were determined. It is indicated that the sample is likely a semiconductor junction, and this structure generates an obvious photovoltaic effect. Spectral responses of photovoltage, cathodotoluminescence and excitation spectra at room temperature were employed to study the structural properties and the mechanism generating photovoltaic effect of the samples. The energy level and the process of electron transition in the ZnO film have also been deduced.

We report the observation of the cathode-ray (CR) pumped ultraviolet (UV) super-radiation luminescence in ZnO thin film at room temperature (RT). The dependence of UV (peak at about 390 nm) and green (peak at about 520 nm) luminescent peaks in ZnO thin film under CR excitation on excitation electron beam current has been investigated. With the increase of the density of excitation electron beam current, green peak relatively decreases and UV peak increases, resulting in a change of the luminescent color from green to blue-purple. The green peak intensity increases sublinearly with the increase of the electron beam current density and saturates at a relatively low density of electron beam current. But the intensity of 390 nm UV peak increases superlinearly with the increase of the electron beam current density. This is a UV super-radiation luminescence of exciton in ZnO under high density pump. In this paper, three-dimensional atomic force microscope images of the surface of unannealled and annealled ZnO films are given.

The cathodoluminescence of ZnO films deposited on Si substrates by reactive dc sputtering is investigated. Apart from the characteristic green emission band (522 nm) of ZnO, an ultraviolet (392 nm) band and a blue (430-460 nm) band have been observed. The x-ray diffraction and cathodoluminescent spectra reveal the dependences of the luminescence on the preparation conditions and crystallinity of the ZnO films.

GaN nanotip triangle pyramids were synthesized on 3C-SiC epilayer via an isoelectronic In-doping technique. The synthesis was carried out in a specially designed two-hot-boat chemical vapor deposition system. In (99.999%) and molten Ga (99.99%) with a mass ratio of about 1:4 were used as the source, and pieces of Si (111) wafer covered with 400-500 nm 3C-SiC epilayer were used as the substrates. The products were analyzed by x-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction, Raman spectroscopy, and photoluminescence measurements. Our results show that the as-synthesized GaN pyramids are perfect single crystal with wurtzite structure, which may have potential applications in electronic/photonic devices.

The present study focuses on the photoluminescence (PL) properties of ZnO films prepared by the reaction of water and zinc. Temperature-dependent PL characteristics of the ZnO films have been investigated in the range from 15 to 260 K. The PL spectrum at 15 K is dominated by neutral donor-bound exciton (D0X) emissions. The emission line at about 3.304 eV can be due to the transition of free electrons to neutral acceptor states (eA0). It is suggested that the ultraviolet emission at room temperature can be attributed to the incorporation of eA0 and free exciton (FX) transitions, rather than sole FX. According to the temperature behavior of green band, it is further confirmed that the green emission is mainly related to the singly ionized oxygen vacancies.

The Ag-doped ZnO films were deposited on Si substrates by dc reactive sputtering. Obvious enhancement of ultraviolet (UV) emission of the samples was observed due to Ag2O nanoclusters formatted during Ag doping. The UV emission consisted of two peaks. The 348nm peak was attributed to Ag2O nanoclusters, and the 382nm one was attributed to ZnO. The strongest UV emission of a certain ZnO–Ag2O film was over ten times stronger than that of a pure ZnO film, which was an exciting result. The enhancement of UV emission was caused by excitons formed at the interface between Ag2O nanoclusters and ZnO grains.

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Temperature-dependent photoluminescence (PL) of nanocrystalline ZnO thin films grown on Si (100) substrates using a sol–gel method has been investigated. From the PL spectra measured in 83–293K, the excitonic emissions and their multiple-phonon replicas have been observed in ultraviolet region, and their origins have been identified. Moreover, it has been found that the temperature dependence of the free exciton peak position can be described by standard expression, and the thermal activation energy extracted from the temperature dependence of the free exciton peak intensity is about 101meV.

The undoping ZnO emitting films were deposited on Si substrates by dc reactive sputtering. There are two peaks of photoluminescence (PL), centered at 3.18 eV (ultraviolet), and at 2.38 eV (green), to be observed in the samples. We investigated the dependence of PL spectra on annealing temperature and annealing atmosphere. According to the calculation of defect levels and the relationship between PL spectra and annealing conditions, we supposed that the green emission of ZnO films corresponds to the local level composed of the antisite defect O Zn .