Structural Characterization and Photoluminescent Properties of Zn1—xMgxO Films on Silicon

Zn1-xMgxO films have been grown on silicon at various substrate temperatures by pulsed laser deposition.The structural and photoluminescent properties of films as a function of substrate temperature have been studied.The optimized substrate temperature is 650℃.The x-ray diffraction spectra indicate that the films are highly C-axis oriented,and no phase separation is observed.The crystal grain size of the films is about 100nm as examined by atomic force microscopy.The cross-sectional transmission electron microscopy verified the C-axis orientation of the Zn1-xMgxO.Thesr films showed ultraviolet photoluminescence at room temperature.The near-band-edge emission peak of the Zn1-xMgxO film deposited at 600℃ has a blueshift (0.40eV) larger than that of the film deposited at 500℃ (0.33eV).The ratio of the near-band-edge to defect level peak intensity is as large as 159.     

Influences of Annealing on Residual Stress and Structure of HfO2 Films

HfO2 films are deposited on BK7 glass substrates by electron beam evaporation. The influences of annealing between 100℃ and 400℃ on residual stresses and structures of HfO2 films are studied. It is found that little differences of spectra, residual stresses and structures are obtained after annealing at lower temperatures. After annealing at higher temperatures, the spectra shift to short wavelength, the residual stress increases with the increasing annealing temperature. At the same time, the crystallite size increases and interplanar distance decreases. The variations of optical spectra and residual stress correspond to the evolutions of structures induced by annealing.     

Influences of Annealing on the Opto—electronic Properties of ZnO Films Grown by Plasma—Enhanced MOCVD

ZnO thin films have been grown on C-plane sapphire substrates by plasma-enhanced metal-organic chemical vapour deposition.The samples are then annealed at a higher temperature.The resistivity,concentration of electron,mobility and optically pumped threshold of both as-grown and annealed films are investigated.Furthermore,their structural and optical properties are also examined with x-ray diffraction,emission spectra and optical transmission spectra.The results indicate that the quality of ZnO thin films can be improved by annealing.     

Electrical and optical properties of Sb-doped ZnO thin films synthesized by sol–gel method

Sb-doped ZnO thin films with different values of Sb content （from 0 to 1.1 at.%） are deposited by the sol-gel dip- coating method under different sol concentrations. The effects of Sb-doping content, sol concentration, and annealing ambient on the structural, optical, and electrical properties of ZnO films are investigated. The results of the X-ray diffraction and ultraviolet-visible spectroscopy （UV-VIS） spectrophotometer indicate that each of all the films retains the wurtzite ZnO structure and possesses a preferred orientation along the c axis, with high transmittance （〉 90%） in the visible range. The Hall effect measurements show that the vacuum annealed thin films synthesized in the sol concentration of 0.75 mol/L each have an adjustable n-type electrical conductivity by varying Sb-doping density, and the photoluminescence （PL） spectra revealed that the defect emission （around 450 nm） is predominant. However, the thin films prepared by the sol with a concentration of 0.25 mol/L, despite their poor conductivity, have priority in ultraviolet emission, and the PL peak position shows first a blue-shift and then a red-shift with the increase of the Sb doping content.     

Effects of Annealing Temperature on Structural and Optical Properties of ZnO Thin Films

The effects of annealing temperature on the structural and optical properties of ZnO films grown on Si （100） substrates by sol-gel spin-coating are investigated. The structural and optical properties are characterized by x-ray diffraction, scanning electron microscopy and photoluminescence spectra. X-ray diffraction analysis shows the crystal quality of ZnO films becomes better after annealing at high temperature. The grain size increases with the temperature increasing. It is found that the tensile stress in the plane of ZnO films first increases and then decreases with the annealing temperature increasing, reaching the maximum value of 1.8 GPa at 700℃. PL spectra of ZnO films annealed at various temperatures consists of a near band edge emission around 380 nm and visible emissions due to the electronic defects, which are related to deep level emissions, such as oxide antisite （OZn）, interstitial oxygen （Oi）, interstitial zinc （Zni） and zinc vacancy （VZn^-）, which are generated during annealing process. The evolution of defects is analyzed by PL spectra based on the energy of the electronic transitions.     

Optical Properties of Co-BaTiO3/Mg（100） Nano-Composite Films Grown by Pulsed Laser Deposition Method

Co nanoparticles embedded in a BaTiO3 matrix, namely Co-BaTiO3 nano-composite films are grown on Mg（100） single crystal substrates by the pulsed laser deposition （PLD） method at 650℃. Optical properties of the CoBaTiO3 nano-composite films are examined by absorption spectra （AS） and photoluminescence （PL） spectra. The results indicate that the concentration of Co nano-particles strongly influences the electron transition of the Co BaTiO3 nano-composite films. The PL emission band ranging from 1.9 to 2.2eV is reported. The AS and PL spectra suggest that the band gap is in the range of 3.28-3.7eV.     

Ultraviolet Luminescence Depending on Zn Interstitial in ZnO Polycrystalline Films

The ultraviolet emission line at 3.315eV is observed at 8K in ZnO polycrystalline films and investigated by temperature-dependent photolumineseence spectra and cathodoluminescence spatial image. The relative intensity of 3.315 eV emission line depends strongly on growth and annealing conditions. The cathodoluminescence image shows that the 3.315 eV emission localizes on the surface and ridge of ZnO grain. These results suggest that the 3.315 eV emission attributes to Zn interstitials at the grain surface and ridge. This emission is stable in the range from 8 K to 300 K and contributes to the room temperature ultraviolet band.     

Characteristics of the crystalline and luminescence properties of a-plane GaN films grown on γ-LiAlO_2(302) substrates

A-plane GaN films are deposited on(302) γ-LiAlO 2 substrates by metalorganic chemical vapor deposition(MOCVD) . The X-ray diffraction(XRD) results indicate that the in-plane orientation relationship between GaN and LAO substrates is [010] LAO [0001] GaN and [203] LAO [1100] GaN with 0.03% and 2.85% lattice mismatch,respectively. Raman scattering results indicate that the strain in the films decreases along with the increase in the thickness of the films. In addition to the band edge emission at 3.42 eV,defects-related luminescence at 3.35 eV is observed in the photoluminescence(PL) spectra. The cathodoluminescence(CL) spectra indicate that the 3.35-eV emission is related to the V pits.     

Structural and electrical characterization of annealed Si1-xCx/SiC thin film prepared by magnetron sputtering

Si-rich Sil-xCx/SiC multilayer thin films are prepared using magnetron sputtering, subsequently followed by thermal annealing in the range of 800-1200 ℃. The influences of annealing temperature （Ta） on the formation of Si and/or SiC nanocrystals （NCs） and on the electrical characteristics of the multilayer film are investigated by using a variety of analytical techniques, including X-ray diffraction （XRD）, Raman spectroscopy and Fourier transform infrared spectrometry （FT-IR）, current-voltage （I-V） technique, and capacitance-voltage （C-V） technique. XRD and Raman analyses indicate that Si NCs begin to form in samples for Ta _ 800 ~C. At annealing temperatures of 1000 ℃ or higher, the formation of Si NCs is accompanied by the formation of SiC NCs. With the increase in the annealing temperature, the shift of FT-IR Si-C bond absorption spectra toward a higher wave number along with the change of band shape can be explained by a Si-C transitional phase between the loss of substitutional carbon and the formation of SiC precipitates and a precursor for the growth of SiC crystalline. The C-V and I-V results indicate that the interface quality of Si1-xCx/SiC multilayer film is improved significantly and the leakage current is reduced rapidly for Ta ≥ 1000 ℃, which can be ascribed to the formation of Si and SiC NCs.     

Effect of High Temperature Annealing on Conduction-Type ZnO Films Prepared by Direct-Current Magnetron Sputtering

We experimentally find that the ZnO thin films deposited by dc-magnetron sputtering have different conduction types after annealing at high temperature in different ambient. Hall measurements show that ZnO films annealed at 1100℃ in N2 and in 02 ambient become n-type and p-type, respectiveIy. This is due to the generation of different intrinsic defects by annealing in different ambient. X-ray photoelectron spectroscopy and photolumineseence measurements indicate that zinc interstitial becomes a main defects after annealing at 1100℃ in N2 ambient, and these defects play an important role for n-type conductivity of ZnO. While the ZnO films annealed at 1100℃ in O2 ambient, the oxygen antisite contributes ZnO films to p-type.     

Effects of annealing rate and morphology of sol–gel derived ZnO on the performance of inverted polymer solar cells

The effects of annealing rate and morphology of sol–gel derived zinc oxide(ZnO)thin films on the performance of inverted polymer solar cells(IPSCs)are investigated.ZnO films with different morphologies are prepared at different annealing rates and used as the electron transport layers in IPSCs.The undulating morphologies of ZnO films fabricated at annealing rates of 10 C/min and 3 C/min each possess a rougher surface than that of the ZnO film fabricated at a fast annealing rate of 50 C/min.The ZnO films are characterized by atomic force microscopy(AFM),optical transmittance measurements,and simulation.The results indicate that the ZnO film formed at 3 C/min possesses a good-quality contact area with the active layer.Combined with a moderate light-scattering,the resulting device shows a 16%improvement in power conversion efficiency compared with that of the rapidly annealed ZnO film device.     

PHOTOLUMINESCENCE OF NANOCRYSTALLINE SiC FILMS PREPARED BY RF MAGNETRON SPUTTERING

Amorphous SiC films are deposited on Si (111) substrates by rf magnetron sputtering and then annealed at 1200℃ for different times by a dc self-heating method in a vacuum annealing system. The crystallization of the amorphous SiC is determined by Raman scattering at room temperature and X-ray diffraction. The experimental result indicates that the SiC nanocrystals have formed in the films. The topography of the as-annealed films is characterized by atomic force microscopy. Measurements of photoluminescence of the as-annealed films show blue or violet light emission from the nanocrystalline SiC films and photoluminescence peak shifts to short wavelength side as the annealing time decreases.     

Effect of high-temperature annealing on AIN thin film grown by metalorganic chemical vapor deposition

The effect of high-temperature annealing on A1N thin film grown by metalorganic chemical vapor deposition was investigated using atomic force microscopy, Raman spectroscopy, and deep ultra-violet photoluminescence （PL） with the excitation wavelength as short as ~ 177 nm. Annealing experiments were carded out in either N2 or vacuum atmosphere with the annealing temperature ranging from 1200 ℃ to 1600 ℃. It is found that surface roughness reduced and compres- sive strain increased with the annealing temperature increasing in both annealing atmospheres. As to optical properties, a band-edge emission peak at 6.036 eV and a very broad emission band peaking at about 4.7 eV were observed in the photoluminescence spectrum of the as-grown sample. After annealing, the intensity of the band-edge emission peak varied with the annealing temperature and atmosphere. It is also found that a much stronger emission band ranging from 2.5 eV to 4.2 eV is superimposed on the original spectra by annealing in either N2 or vacuum atmosphere. We attribute these deep-level emission peaks to the VAL--ON complex in the A1N material.     

Optical properties of ZnO thin films on SiO_2 substrates deposited by radio frequency magnetron sputtering

The optical properties of both the annealed and as-deposited ZnO thin films by radio frequency (RF) magnetron sputtering on SiO2 substrates were studied. In the annealed films, two pronounced well defined exciton absorption peaks for the A and B excitons were obtained in the absorption spectra, a strong free exciton emission without deep-level emissions was observed in the photoluminescence (PL) spectra at room temperature. It was found that annealing the films in oxygen dramatically improved the optical properties and the quality of the films.     

Microstructure and photoluminescence of Er-doped SiOx films synthesized by ion beam assisted deposition

Er-doped SiO_x films were synthesized at 500℃ by ion beam assisted deposition technique and annealed at 800 and 1100℃ for 2h in the air atmosphere. The analysis by using energy dispersive x-ray spectroscopy showed that the ratio of Si to O decreased from 3 in the as-deposited films to about 1 in the annealed films. The investigation by using transmission electron microscopy and x-ray diffraction indicated that annealing induces a microstructure change from amorphous to crystalline. The grain sizes in the films were about 10 and 40nm when annealed at 800 and 1100℃, respectively. The films annealed at temperatures of 800 and 1100℃ exhibited a sharp photoluminescence (PL) at 1.533μm from the Er centres when pumped by 980nm laser. The influence of microstructure and grain size on the PL from Er-doped SiO_x films has been studied and discussed.     

Effects of Annealing on Microstructure and Optical Properties of TiO2 Sculptured Thin Films

The evolution of microstructure and optical properties of TiO2 sculptured thin films under thermal annealing is reported. XRD, field emission SEM, UV-Vis-NIR spectra are employed to characterize the microstructural and optical properties. It is found that the optimum annealing temperature for linear birefringence is 500℃. The maximum of transmission difference for linear birefringence is up to 18%, which is more than twice of that in as-deposited thin films. In addition, the sample annealed at 500℃ has a minimum of column angle about 12℃. The competitive process between the microstructural and optical properties is discussed in detail. Post-annealing is a useful method to improve the linear birefringence in sculptured thin films for practical applications.     

Study on optical anisotropy properties of SiO2 films with different thermal annealing temperatures

SiO2 films are deposited on Si substrates by an ion beam sputtering technique and continuously annealed in a quartz culture dish in air at various annealing temperature ranging from 20 to 750 ℃ with a step of 100 ℃ for a fixed time of 24 h. The effects of thermal treatment on optical anisotropy properties of SiO2 films are investigated by spectroscopic ellipsometry. When the annealing temperature is 550℃, the optical anisotropy properties of SiO2 film is minimum. The obtained results indicate that the optical anisotropy properties of SiO2 films can be improved by a proper thermal annealing process.     

Effects of high-dose Ge ion implantation and post-implantation annealing on ZnO thin films

This paper reports that ion implantation to a dose of 1×10¹⁷ ions/cm² was performed on c-axis-orientated ZnO thin films deposited on (0001) sapphire substrates by the sol-gel technique. After ion implantation, the as-implanted ZnO films were annealed in argon ambient at different temperatures from 600-900℃. The effects of ion implantation and post-implantation annealing on the structural and optical properties of the ZnO films were investigated by x-ray diffraction (XRD), photoluminescence (PL). It was found that the intensities of (002) peak and near band edge (NBE) exitonic ultraviolet emission increased with increasing annealing temperature from 600-900℃. The defect related deep level emission (DLE) firstly increased with increasing annealing temperature from 600- 750℃, and then decreased quickly with increasing annealing temperature. The recovery of the intensities of NBE and DLE occurs at \sim 850℃ and \sim 750℃ respectively. The relative PL intensity ratio of NBE to DLE showed that the quality of ZnO films increased continuously with increasing annealing temperature from 600 - 900℃.     

Effect of high-temperature annealing on AlN thin film grown by metalorganic chemical vapor deposition

The effect of high-temperature annealing on AlN thin film grown by metalorganic chemical vapor deposition was investigated using atomic force microscopy, Raman spectroscopy, and deep ultra-violet photoluminescence(PL) with the excitation wavelength as short as ～ 177 nm. Annealing experiments were carried out in either N2 or vacuum atmosphere with the annealing temperature ranging from 1200℃ to 1600℃. It is found that surface roughness reduced and compressive strain increased with the annealing temperature increasing in both annealing atmospheres. As to optical properties,a band-edge emission peak at 6.036 eV and a very broad emission band peaking at about 4.7 eV were observed in the photoluminescence spectrum of the as-grown sample. After annealing, the intensity of the band-edge emission peak varied with the annealing temperature and atmosphere. It is also found that a much stronger emission band ranging from 2.5 eV to 4.2 eV is superimposed on the original spectra by annealing in either N2 or vacuum atmosphere. We attribute these deep-level emission peaks to the VAL–ONcomplex in the AlN material.     

Influences of high-temperature annealing on atomic layer deposited Al2 O3/4H-SiC

High-temperature annealing of the atomic layer deposition (ALD) of Al2O3 films on 4H-SiC in O 2 atmosphere is studied with temperature ranging from 800℃ to 1000℃. It is observed that the surface morphology of Al2O3 films annealed at 800℃ and 900℃ is pretty good, while the surface of the sample annealed at 1000℃ becomes bumpy. Grazing incidence X-ray diffraction (GIXRD) measurements demonstrate that the as-grown films are amorphous and begin to crystallize at 900℃. Furthermore, C-V measurements exhibit improved interface characterization after annealing, especially for samples annealed at 900℃ and 1000℃. It is indicated that high-temperature annealing in O2 atmosphere can improve the interface of Al2O3 /SiC and annealing at 900℃ would be an optimum condition for surface morphology, dielectric quality, and interface states.