InGaZnO thin films grown by pulsed laser deposition

We fabricated InGaZnO (IGZO) ceramic target (In: Ga: Zn = 1: 1: 4 in atomic ratio) using solid-state reaction at ambient atmosphere, and deposited IGZO thin films on quartz glass at room temperature under various oxygen partial pressures using the pulsed laser deposition method. Influence of oxygen pressure on crystal structure, surface morphology, optical and electrical properties were investigated. It was found that all the films deposited at room temperature exhibit amorphous structure. On the other hand, the physical properties of the films like transparency, electron mobility, and free-electron concentration were found to be correlated to the oxygen pressure during the deposition and in turn to the possible oxygen vacancies or metallic interstitials in the films. The analysis of X-ray photoelectron spectra (XPS) of the films indicated that there are no metallic 3d states of In, Ga and Zn, suggesting that oxygen vacancies could be main defects that affect physical properties of the films.     

Study of manganese oxide thin films grown by pulsed laser deposition

In this paper, we report on the growth of manganese oxides thin films by Pulsed Laser Deposition using an MnO target at various oxygen pressures and substrate temperatures ranging from 550 to 800 °C. Grazing Incidence X-Ray Diffraction measurements on the grown films revealed that, at low deposition temperature, the dominant phase is Mn₂O₃, but as the deposition temperature was raised above 700 °C, a phase transformation occurred leading to the formation of Mn₃O₄. In a qualitative comparison, in the temperature range of 500-850 °C, and at a pressure below 13 Pa, the phase diagram of bulk manganese oxides and our grown films show a fair correlation. The films grown near the transition temperature (T = 700 °C) were found to be very thin compared to those grown at lower or higher temperatures, but the surface roughness was found to increase with temperature, as determined by Atomic Force Microscopy.     

A parametric study of AlN thin films grown by pulsed laser deposition

High quality AlN thin films were grown at 200–450°C on sapphire substrates by laser ablation of Al targets in nitrogen reactive atmosphere. The nitrogen pressure was varied between 10⁻³ and 10⁻¹ mbar. The reactive gas pressure during irradiation and the temperature of the substrate were found to essentially influence the quality of the layers. X-ray diffraction analysis evidenced the formation of highly orientated layers for a very restrictive set of parameters. Other analysis techniques, like X-ray photoelectron spectroscopy, secondary ion mass spectroscopy, optical transmission spectroscopy have been used to evidence the good stoichiometry and purity of the films. The characteristics of these films were compared with those of AlN thin films deposited in similar experimental conditions, on Si (100) and Si (111) substrates.     

Low-temperature deposition of iridium thin films by pulsed laser deposition

Extremely smooth iridium (Ir) thin films were deposited on Si(1 0 0) substrate at lower temperature than 300 °C by pulsed laser deposition (PLD) technique using Ir target in a vacuum atmosphere. The crystal orientation, surface morphology, and resistivity of the Ir thin films were systematically determined as a function of substrate temperature. Well-crystallized and single-phase Ir thin films with (1 1 1) preferred orientation were obtained at substrate temperature of 200-300 °C. The surface roughness increased with the increasing of substrate temperature. Likewise, the room-temperature resistivity of Ir thin films decreased with increasing substrate temperature, showing a low value of (10.7±0.1) μΩ cm at 300 °C.     

ZnO thin films prepared by pulsed laser deposition

Zinc oxide (ZnO) thin films were deposited on soda lime glass substrates by pulsed laser deposition (PLD) in an oxygen-reactive atmosphere. The structural, optical, and electrical properties of the as-prepared thin films were studied in dependence of substrate temperature and oxygen pressure. High quality polycrystalline ZnO films with hexagonal wurtzite structure were deposited at substrate temperatures of 100 and 300 °C. The RMS roughness of the deposited oxide films was found to be in the range 2-9 nm and was only slightly dependent on substrate temperature and oxygen pressure. Electrical measurements indicated a decrease of film resistivity with the increase of substrate temperature and the decrease of oxygen pressure. The ZnO films exhibited high transmittance of 90% and their energy band gap and thickness were in the range 3.26-3.30 eV and 256-627 nm, respectively.     

Effects of stress on the structure of indium-tin-oxide thin films grown by pulsed laser deposition

The effects of stress in pulsed laser deposited (PLD) indium-tin-oxide (ITO) films formed on glass substrate at 200 °C and oxygen pressures (P_{o 2}) ranging from 0.1 to 2.7 Pa are discussed. Grazing incidence X-ray diffraction (GIXRD) investigations of the ITO films show splitting of the diffraction peaks and significant changes in the lattice constants for films deposited at low P_{o 2} and when the thickness of the films is larger than 150 nm. These features were due to intrinsic stress caused by the incidence of energetic particles on the substrate during growth. The splitting of the peaks only occurred in the bulk of the films, while near the surface, single peaks were evidenced, indicating the existence of two layers. No apparent splitting of the diffraction peaks or shifts in peak positions occurred in the ITO layers with thickness less than 100 nm. In spite of the presence of stress in the ITO films, resistivity less than 3 10, ^-4 cm was obtained. © 2001 Kluwer Academic Publishers     

脉冲激光沉积制备立方AlN薄膜的研究

采用脉冲激光沉积(PLD)方法,在SrTiO3(100)衬底上在650℃、10Pa N2条件下成功制备了立方结构的AlN薄膜.高能电子衍射(RHEED)及X射线衍射(XRD)分析表明立方AlN和SrTiO3的外延关系为AlN[100]∥SrTiO3[100]和AlN(200)∥SrTiO3(100).其AlN(200)衍射峰的摇摆曲线半高宽(FWHM)为0.44°,说明薄膜结晶性能良好.原子力显微镜(AFM)表明外延的立方AlN薄膜表面具有原子级平整度,其表面均方根粗糙度(RMS)为0.674nm.通过X光电子能谱(XPS)分析AlN薄膜表面成分,结果表明AlN薄膜表面没有被氧化.     

Structural and optical properties of neodymium-doped lutetium fluoride thin films grown by pulsed laser deposition

Neodymium-doped lutetium fluoride (Nd³⁺:LuF₃) thin films were successfully grown on MgF₂ (0 0 1) substrates by pulsed laser deposition (PLD). It is void of cracks that are otherwise prevalent due to structural phase transitions in Nd³⁺:LuF₃ during thin film deposition and bulk crystal growth. Cathodoluminescence (CL) spectra revealed multiple emission peaks, with a dominant peak in the vacuum ultraviolet (VUV) region at 179 nm. This peak has a decay time of 6.7 ns. The ability to grow high quality Nd³⁺-doped fluoride thin films would enable fabrication of VUV light-emitting devices that will enhance applications requiring efficient VUV light sources.     

ITO thin films deposited by advanced pulsed laser deposition

Indium tin oxide thin films were deposited by computer assisted advanced PLD method in order to obtain transparent, conductive and homogeneous films on a large area. The films were deposited on glass substrates. We studied the influence of the temperature (room temperature (RT)-180 °C), pressure (1-6 × 10^− 2 Torr), laser fluence (1-4 J/cm²) and wavelength (266-355 nm) on the film properties. The deposition rate, roughness, film structure, optical transmission, electrical conductivity measurements were done. We deposited uniform ITO thin films (thickness 100-600 nm, roughness 5-10 nm) between RT and 180 °C on a large area (5 × 5 cm²). The films have electrical resistivity of 8 × 10^− 4 Ω cm at RT, 5 × 10^− 4 Ω cm at 180 °C and an optical transmission in the visible range, around 89%.     

脉冲激光沉积法制备Pt薄膜的研究

采用脉冲激光沉积技术在(0001)取向的蓝宝石基片上外延生长了Pt单晶薄膜,研究了沉积温度和激光能量对Pt薄膜的晶体结构,表面形貌及电学性能的影响规律.X射线衍射(XRD)分析结果表明,在沉积温度650℃、激光脉冲频率1Hz和激光能量280mJ的条件下,制备得到的Pt(111)单晶薄膜,其(111)面ω摇摆曲线半高宽(FWHM)仅为0.068°.原子力显微镜(AFM)分析表明外延的Pt薄膜表面具有原子级平整度,其表面均方根粗糙度(RMS)约为1.776nm.四探针电阻测试结果显示薄膜方阻为1/962Ω/□,满足铁电薄膜的制备工艺对Pt底电极的要求.     

Transparent conducting F-doped SnO2 thin films grown by pulsed laser deposition

Transparent conducting fluorine-doped tin oxide (SnO₂:F) films have been deposited on glass substrates by pulsed laser deposition. The structural, electrical and optical properties of the SnO₂:F films have been investigated as a function of F-doping level and substrate deposition temperature. The optimum target composition for high conductivity was found to be 10 wt.% SnF₂ + 90 wt.% SnO₂. Under optimized deposition conditions (T_s = 300 °C, and 7.33 Pa of O₂), electrical resistivity of 5 × 10^− 4 Ω-cm, sheet resistance of 12.5 Ω/□, average optical transmittance of 87% in the visible range, and optical band-gap of 4.25 eV were obtained for 400 nm thick SnO₂:F films. Atomic force microscopy measurements for these SnO₂:F films indicated that their root-mean-square surface roughness ( 6 Å) was superior to that of commercially available chemical vapor deposited SnO₂:F films ( 85 Å).     

ZnO thin films grown on platinum (111) buffer layers by pulsed laser deposition

C-axis oriented ZnO layers were grown by pulsed-laser deposition on the surface of a platinum (111) epitaxial thin film supported by a c-sapphire substrate. The Pt bottom layer provides good in-plane lattice matching with c-ZnO, enabling epitaxial re-growth of the latter, as shown by X-ray diffraction data. Room- and low-temperature reflectance and photoluminescence measurements have been performed on such ZnO/Pt heterostructures for the first time. Intense resonances, corresponding to the A and B free excitons, are clearly evidenced in the reflectance measurements at 30 K, while the deconvolved full widths at half maximum of the bound excitonic lines, observed in the photoluminescence spectra at 28 K, range between 3 and 7 meV. This report clearly demonstrates that ZnO epitaxial thin films with very good structural and optical properties can be grown on a Pt bottom electrode and, thus, establishes the potential of this material system for use in ZnO-based optoelectronic devices.     

Production of porous carbon thin films by pulsed laser deposition

Pulsed laser deposition (PLD) has been used together with the Glancing Angle Deposition (GLAD) technique [1 and 2] for the first time to produce highly porous structured films. A laser produced carbon plasma and vapour plume was deposited at a highly oblique incident angle onto rotating Si substrates, resulting in films exhibiting high bulk porosity and controlled columnar microstructure. By varying the substrate rotation rate, the shape of the microcolumns can be tailored. These results extend the versatility of the GLAD process to materials not readily deposited by means of traditional physical vapour deposition techniques.     

On the optical properties of bismuth oxide thin films prepared by pulsed laser deposition

The optical properties of bismuth oxide films prepared by pulsed laser deposition (PLD), absorption in the photon energy range 2.50-4.30 eV and optical functions (n, k, ?₁, and ?₂) in the domain 3.20-6.50 eV, have been investigated. As-prepared films (d=0.05-1.50 μm) are characterized by a mixture of polycrystalline and amorphous phases. The fundamental absorption edge is described by direct optical band-to-band transitions with energies 2.90 and 3.83 eV. The dispersion of the optical functions provided values of 4.40-6.25 eV for electron energies of respective direct transitions. In the spectral range 400-1000 nm, bismuth oxide films show a normal dispersion, which can be interpreted in the frame of a single oscillator model.     

Structural investigations of InZnO films grown by pulsed laser deposition technique

Thin films of indium zinc oxide were grown from targets with In atomic concentration [In/(In + Zn)] of 2.8%, 4.3%, and 16.8%, respectively, by pulsed laser deposition technique (KrF laser, 10 Hz, 4 J/cm² fluence) on Si(001) and glass substrates that were heated at 500 °C. X-ray diffraction investigations showed that targets that had an atomic In concentration of 2.8% exhibited only the wurtzite-type ZnO lattice, while the targets that contained In concentrations of 4.3% and 16.8% consisted of a mixture of the wurtzite-type ZnO and the homologous compound Zn₇In₂O₁₀. All deposited films exhibited only the wurtzite-type ZnO lattice, being c-axis textured. The increase of the In concentration resulted in films less textured that also exhibited increased lattice parameters a and c. X-ray photoelectron spectroscopy investigations showed slight changes of the In 3d and Zn 2p binding energies for increased In content, consistent with an In doped ZnO lattice.     

Microstructure of homoepitaxial strontium titanate films grown by pulsed laser deposition

Homoepitaxial strontium titanate (SrTiO₃) thin films have been grown by pulsed laser deposition in order to identify those defects which are intrinsic to the growth of SrTiO₃. The pulse rate and oxygen annealing pressure were varied, although the oxygen pressure had no effect under these conditions. Columnar growth was common. The nature of the columns is described, but the reason for their presence is not fully understood. They can be suppressed using a high laser pulse rate.     

Nano-polycrystalline vanadium oxide thin films prepared by pulsed laser deposition

Nano-polycrystalline vanadium oxide thin films have been successfully produced by pulsed laser deposition on Si(100) substrates using a pure vanadium target in an oxygen atmosphere. The vanadium oxide thin film is amorphous when deposited at relatively low substrate temperature (500 degrees C) and enhancing substrate temperature (600-800 degrees C) appears to be efficient in crystallizing VOx thin films. Nano-polycrystalline V3O7 thin film has been achieved when deposited at oxygen pressure of 8 Pa and substrate temperature of 600 degrees C. Nano-polycrystalline VO2 thin films with a preferred (011) orientation have been obtained when deposited at oxygen pressure of 0.8 Pa and substrate temperatures of 600-800 degrees C. The vanadium oxide thin films deposited at high oxygen pressure (8 Pa) reveal a mix-valence of V5+ and V4+, while the VOx thin films deposited at low oxygen pressure (0.8 Pa) display a valence of V4+. The nano-polycrystalline vanadium oxide thin films prepared by pulsed laser deposition have smooth surface with high qualities of mean crystallite size ranging from 30 to 230 nm and Ra ranging from 1.5 to 22.2 nm. Relative low substrate temperature and oxygen pressure are benifit to aquire nano-polycrystalline VOx thin films with small grain size and low surface roughness.     

Microstructural evolution in lubricious ZnO films grown by pulsed laser deposition

Zinc oxide (ZnO) is well known to the electronic industry as a piezoelectric material. Recent research from this laboratory also indicates the potential of ZnO as a tribological material. The current work describes the evolution of microstructure with deposition parameters in pulsed laser deposited ZnO thin films, specifically targeted for friction and wear applications. Films were characterized by high resolution scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Friction and wear measurements were made using a ball-on-disk tribometer. Films were grown in vacuum (V) as well as in 5 mTorr of oxygen (O₂), while the substrates were kept at room temperature (RT). The RT/V ZnO films have (002) columnar texture with an average column width of 20 nm. The RT/O₂ films also are nanoclumnar with (002) texture, but each column is a mosaic of low-angle boundaries. Deformation mechanisms associated with nanocrystalline grain structure were analyzed with particular reference to sliding contact. Mechanisms to provide the observed low friction of RT/O₂ films (μ=0.15–0.20) have been activated by its mosaic structure.     

Nonlinear optical properties of thin iron films grown on MgO (100) by pulsed laser deposition

Thin films of iron were fabricated on MgO (100) substrates using pulsed laser deposition technique. The crystalline property and surface roughness of the films were investigated by X-ray diffraction and atomic force microscopy, respectively. It was found that the morphology of the Fe film deposited at room temperature was characteristic of continuous metal film. Increasing the deposition temperature caused the smooth Fe film to break up, and nanoscale Fe islands were formed. We performed the z-scan measurements to study the third-order optical nonlinearity of the continuous approximately 9-nm-thick iron film. The results show that the ultrathin iron film exhibits large nonlinear refractive coefficient, n₂=7.09×10⁻⁵ cm²/kW, and nonlinear absorption coefficient, β=−5.52×10⁻³ (cm/W), at the wavelength of 532 nm.