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.     

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.     

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.     

Structural properties of cobalt ferrite thin films deposited by pulsed laser deposition: Effect of the reactive atmosphere

Cobalt ferrite thin films have been elaborated by pulsed laser ablation of a CoFe₂ metallic target on Si (100) substrates. The films were deposited at low temperature (300 °C) in various pressures of two different reactive atmospheres (O₂/N₂, 20:80 and O₂). We present the influence of the nature of the reactive gas and of the deposition pressure on the crystallisation. It has been shown that a strong (111) preferential orientation is obtained for intermediate pressures of the O₂/N₂ reactive gas. The degree of orientation is higher for the O₂/N₂ mixture than for pure O₂. This behaviour is explained in terms of kinetic energy of the deposited species.     

Structural and magnetic properties of Co-Ga co-doped ZnO thin films fabricated by pulsed laser deposition

Co-Ga co-doped ZnO films were fabricated by pulsed laser deposition on quartz substrates. The obtained films exhibited a wurtzite structure with c-axes growth preference. Optical measurements showed the presence of the cobalt ions in a tetrahedral crystal field, which proved that the Co ion substitution in the ZnO lattice, acting as magnetic cation. Hall measurements indicated that the films were n-type conductive with the electron concentrations of ~ 10²⁰/cm³. This value was much higher than that of the Co-doped films, suggesting the effective incorporation of Ga in the films. Room temperature ferromagnetism was observed for the Ga-Co co-doped thin films.     

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%.     

High quality amorphous indium zinc oxide thin films synthesized by pulsed laser deposition

Indium zinc oxide films were grown from targets with two different In atomic concentration [In/(In + Zn)] of 40% and 80% by the pulsed laser deposition technique on glass substrates from room temperature up to 100 °C. X-ray diffraction and reflectometry investigations showed that films were amorphous and dense. Thin films (thickness < 100 nm) exhibited higher optical transmittance and resistivities than thick films (thickness > 1000 nm), probably caused by a significant decrease of oxygen vacancies due to atmosphere exposure. Films deposited from the In rich target under an oxygen pressure of 1 Pa exhibited optical transmittance higher than 85%, resistivities around 5- 7 × 10^− 4 Ω cm and mobilities in the 47-54 cm²/V s range.     

Controlled growth and characteristics of single-phase Cu2O and CuO films by pulsed laser deposition

Copper oxide, Cu₂O and CuO, thin films have been synthesized on Si (100) substrates using pulsed laser deposition method. The influences of substrate temperature and oxygen pressure on the structural properties of copper oxide films were discussed. The X-ray diffraction results show that the structure of the films changes from Cu₂O to CuO phase with the increasing of the oxygen pressure. It is also found that the (200) and (111) preferred Cu₂O films can be modified by changing substrate temperature. The formation of Cu₂O and CuO films are further identified by Fourier transform infrared spectroscopy. For the Cu₂O films, X-ray photoelectron spectroscopic studies indicate the presence of CuO on the surface. In addition, the optical gaps of Cu₂O and CuO films have been determined by measuring the transmittance and reflectance spectra.     

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.     

A study of microstructural and optical properties of nanocrystalline ceria thin films prepared by pulsed laser deposition

Thin films of cerium oxide (CeO₂) have been deposited on (100) Si substrates using pulsed laser deposition technique at various substrate temperatures from room temperature (RT) to 973 K at an optimized oxygen partial pressure of 3 Pa. Structural, morphological and optical properties have been carried out using X-ray diffraction (XRD), Raman, ellipsometry and atomic force microscopy techniques. XRD results showed that the deposited films are polycrystalline with cubic structure. At room temperature, the film showed preferred orientation along (111) plane, while at higher temperatures, it exhibited preferred orientation along (200). The crystallite sizes were calculated and were found to be in the range 17-52 nm. The texture coefficient for (200) reflection increased until 573 K, and then decreased in the temperature range 673-973 K. The Raman peak appeared at 463 cm^− 1 due to the F_2g active mode also confirmed the formation of CeO₂ with a cubic structure. There was a systematic variation in the Raman peak intensity, frequency shift and line broadening with the increase of temperature. The ellipsometry studies showed that the refractive index and band gap increased from 2.2 to 2.6 and 3.4 to 3.6 eV, respectively with increasing substrate temperature from RT to 973 K.     

Composition controlling of KNbO3 thin films prepared by pulsed laser deposition

The composition of KNbO₃ thin films prepared by pulsed laser deposition is crucially influenced by the deposition configuration. In the present study, the composition of KNbO₃ thin films grown on Si (100) substrates by pulsed laser ablation was tried to be controlled by adjusting the target-substrate distance and the oblique angle of substrate from the plume axial direction. It was found that the K deficiency in the films can be effectively avoided by setting the substrate at an appropriate oblique angle from the plume axial direction. The stoichiometric KNbO₃ thin films with a K/Nb molar ratio of 0.98 were successfully obtained, where the substrates were set at an oblique angle of 3-12° from the plume axis while the target-substrate distance was kept at 40 mm.     

Microstructure of Mg-Zn-Ca thin film derived by pulsed laser deposition

Mg₆₀Zn_40−хCa_х (х = 5, 3, 1) powders and thin films have been produced by high energy mechanical alloying (HEMA) and pulsed laser deposition (PLD), respectively and the influence of PLD processing parameters on the microstructures of the Mg-Zn-Ca amorphous thin film was investigated using XRD, TEM, HRTEM and XEDS. Amorphous powder and thin film corresponding to Mg₆₀Zn₃₅Ca₅ composition have been successfully generated. The substrate temperature appears to be the dominant PLD processing parameter among others contributing to the formation of amorphous thin film.     

Correlations between optical properties, microstructure, and processing conditions of Aluminum nitride thin films fabricated by pulsed laser deposition

Aluminum nitride (AlN) films were deposited using pulsed laser deposition (PLD) onto sapphire (0001) substrates with varying processing conditions (temperature, pressure, and laser fluence). We have studied the dependence of optical properties, structural properties and their correlations for these AlN films. The optical transmission spectra of the produced films were measured, and a numerical procedure was applied to accurately determine the optical constants for films of non-uniform thickness. The microstructure and texture of the films were studied using various X-ray diffraction techniques. The real part of the refractive index was found to not vary significantly with processing parameters, but absorption was found to be strongly dependent on the deposition temperature and the nitrogen pressure in the deposition chamber. We report that low optical absorption, textured polycrystalline AlN films can be produced by PLD on sapphire substrates at both low and high laser fluence using a background nitrogen pressure of 6.0 × 10^− 2 Pa (4.5 × 10^− 4 Torr) of 99.9% purity.     

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.     

Structural and optical properties of tellurite thin film glasses deposited by pulsed laser deposition

Tellurite (TeO₂-TiO₂-Nb₂O₅) thin film glasses have been produced by pulsed laser deposition at room temperature at laser energy densities in the range of 0.8-1.5 J/cm² and oxygen pressures in the range of 3-11 Pa. The oxygen concentration in the films increases with laser energy density to reach values very close to that of the bulk glass at 1.5 J/cm², while films prepared at 1.5 J/cm² and pressures above 5 Pa show oxygen concentration in excess of 10% comparing to the glass. X-ray photoelectron spectroscopy shows the presence of elementary Te in films deposited at O₂ pressures ≤ 5 Pa that is not detected at higher pressures, while analysis of Raman spectra of the samples suggests a progressive substitution of TeO₃ trigonal pyramids by TeO₄ trigonal bipyramids in the films when increasing their oxygen content. Spectroscopic ellipsometry analysis combined with Cauchy and effective medium modeling demonstrates the influence of these compositional and structural modifications on the optical response of the films. Since the oxygen content determines their optical response through the structural modifications induced in the films, those can be effectively controlled by tuning the deposition conditions, and films having large n (2.08) and reduced k (< 10^− 4) at 1.5 μm have been produced using the optimum deposition conditions.     

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.     

脉冲激光沉积制备的HfO2薄膜的结构与电学性能

采用脉冲激光沉积（PLD）方法在Si（100）基底上制备了有效氧化层厚度为8．6nm，介电常数为29．3的HfO2薄膜．借助C射线衍射（XRD）、原子力显微镜（AFM）、高分辨透射电镜（HRTEM）分析了样品的微观结构，对电容的C-V与I-V电学特性进行了测试。实验结果表明，该方法制得的HfO2薄膜表面光滑，N2500℃下退火30mm后样品表面粗糙度由0．203nm变为0．498nm，薄膜由非晶转变为简单正交结构，界面层得到有效控制，该栅介质电容具有良好的C-V特性，较低的漏电流密度（4．3×10^-7A/cm^2，@-1V），是SiO2栅介质的理想替代物．     

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.     

Synthesis of SrSnO3 thin films by pulsed laser deposition: Influence of substrate and deposition temperature

SrSnO₃ thin films were prepared by pulsed laser deposition on amorphous silica and single crystal substrates of R-sapphire, (100)LaAlO₃ and (100)SrTiO₃. High quality epitaxial (100) oriented films were obtained on LaAlO₃ and SrTiO₃ while a texture was revealed for films on sapphire deposited at the same deposition temperature of 700 °C. Amorphous films were obtained on silica but a post annealing at 800 °C induced crystallization with a random orientation. The screening of deposition temperature showed epitaxial features on SrTiO₃ from 650 °C while no crystallization was observed at 600 °C. The influence of substrate and deposition temperature was confirmed by Scanning Electron Microscopy and Atomic Force Microscopy observations.     

Comparison of high-pressure dc-sputtering and pulsed laser deposition of superconducting YBa2Cu3O x thin films

Superconducting YBa₂Cu₃O_x thin films were deposited on NdGaO₃ (110) substrates using two different techniques: dc sputtering at high oxygen pressure and pulsed laser deposition. The structure, electrical properties, and surface morphology of the obtained films were compared. The superior crystal quality of dc-sputtered films fabricated at the same temperature and at oxygen pressure of the same range as for laser-deposited films can be explained by a lower deposition rate providing time for recrystallization processes. The re-evaporation becomes significant for dc sputtering at high deposition temperatures and results in Badeficient films. The high mobility of atoms on the surface of the growing film during laser deposition helps in the formation of smoothc-oriented areas of the film.