Time resolved calorimetry of te films during pulsed laser annealing

Using a pyroelectric thin-film calorimeter the temperature of 30 nm thick Te films during pulsed laser annealing was studied in real-time. A XeCl excimer laser pumped dye laser with Raman shifter was utilized to study the wavelength and energy dependence. No significant wavelength dependence was noticed. Depending on the pulse energy, however, melting, boiling and crystallization of the Te films was observed. These findings support a strictly thermal model for laser annealing and optical recording with Te based media. In addition boiling was identified as the prevalent mechanism for the loss of material.     

Structural and optical properties of pulsed laser deposited ZnO thin films

Nanocrystalline ZnO thin films were grown by means of pulsed laser deposition. The ablation process was carried out at relatively low background oxygen gas pressure (10 Pa) and by varying the substrate temperature up to 600 °C. Information on the structural and morphological properties of the deposited thin films have been obtained by means of X-ray photoelectron, Raman spectroscopies, X-ray diffraction (XRD) and atomic force microscopy (AFM). The results showed that all the deposited films are sub-stoichiometric in oxygen and with a hexagonal wurtzite crystalline structure, characterized by features of some tens of nanometers in size. An improvement of the films' crystalline quality was observed for the deposition temperature of 300 °C while the further increase of the deposition temperature up to 600 °C induces a worsening of the material's structural properties with the development of a large amount of nanoparticle's clusters. The analysis of the XRD patterns shows a growth crystallographic preferential direction as a function of the deposition temperature, in agreement with the appearance of the only E₂ optical phonon mode in the Raman spectra. Such findings are compatible with the changes observed in the photoluminescent (PL) optical response and was related to the modification of the ZnO thin film structural quality.     

Preparation and some properties of pulsed laser deposited YFeO3 films

YFeO₃ orthoferrite films have been deposited on to quartz and sapphire substrates by pulsed laser deposition. The films crystallize when annealed at temperatures in the range 750 to 900°C. The perpendicular hysteresis loops are rectangular with a maximum coercivity of 9 kOe. The Faraday rotation at 633 nm wavelength is in the range 4–5 × 10³ deg/cm.     

脉冲准分子激光淀积薄膜的实验研究

利用两种脉宽 (30ns,5 0 0fs)的KrF准分子激光展开了淀积类金刚石薄膜的实验研究 ,并且成功地制备了大面积不含氢成分的HF DLC薄膜 ,运用时空分辨的等离子体发射光谱诊断系统和离子探针系统研究了等离子体特性对薄膜性能的影响。尝试了利用准分子激光制备非晶硅薄膜 ,研究了实验参数对非晶硅薄膜制备的影响 ,并分析了制备具有良好电学和光学性能的非晶硅薄膜的条件     

Effects of laser fluence on the structural properties of pulsed laser deposited ruthenium thin films

Ruthenium (Ru) has received great interest in recent years for applications in microelectronics. Pulsed laser deposition (PLD) enables the growth of Ru thin films at low temperatures. In this paper, we report for the first time the characterization of pulsed laser deposited Ru thin films. The deposition processes were carried out at room temperature in vacuum environment for different durations with a pulsed Nd:YAG laser of 355-nm laser wavelength, employing various laser fluences ranging from 2 J/cm² to 8 J/cm². The effect of the laser fluence on the structural properties of the deposited Ru films was investigated using surface profilometry, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Ru droplets, some spherical in shape and some flattened into round discs were found on the deposited Ru. The droplets were correlated to ripple formations on the target during the laser-induced ejection from the target. In addition, crystalline Ru with orientations of (100), (101), and (002) was observed in the XRD spectra and their intensities were found to increase with increasing laser fluence and film thickness. Grain sizes ranging from 20 nm to 35 nm were deduced using the Scherrer formula. Optical emission spectroscopy (OES) and energy-dispersive X-ray spectroscopy (EDS) show that the composition of the plume and the deposited Ru film was of high purity.     

Effect of annealing on thermal stability and morphology of pulsed laser deposited Ir thin films

Iridium (Ir) thin films, deposited on Si (1 0 0) substrate by pulsed laser deposition (PLD) technique using Ir target in a vacuum atmosphere, were annealed in air ambient and the thermal stability was investigated. The crystal structure and surface morphology of Ir thin films before and after being annealed were studied by X-ray diffraction, Raman scattering, scanning electron microscope, and atomic force microscopy. The results showed that single-phase Ir thin films with (1 1 1) preferred orientation could be deposited on Si (1 0 0) substrate at 300 °C and it remained stable below 600 °C, which showed a promising bottom electrode of integrated ferroelectric capacitors. Ir thin films got oxidized to IrO₂ at temperatures from 650 to 800 °C.     

Tribological properties of diamond-like carbon films deposited by pulsed laser arc deposition

A novel method, pulsed laser arc deposition combining the advantages of pulsed laser deposition and cathode vacuum arc techniques, was used to deposit the diamond-like carbon (DLC) nanofilms with different thicknesses. Spectroscopic ellipsometer, Auger electron spectroscopy, x-ray photoelectron spectroscopy, Raman spectroscopy, atomic force microscopy, scanning electron microscopy and multi-functional friction and wear tester were employed to investigate the physical and tribological properties of the deposited films. The results show that the deposited films are amorphous and the sp$^{2}$, sp$^{3}$ and C--O bonds at the top surface of the films are identified. The Raman peak intensity and surface roughness increase with increasing film thickness. Friction coefficients are about 0.1, 0.15, 0.18, when the film thicknesses are in the range of 17--21~nm, 30--57~nm, 67--123~nm, respectively. This is attributed to the united effects of substrate and surface roughness. The wear mechanism of DLC films is mainly abrasive wear when film thickness is in the range of 17--41~nm, while it transforms to abrasive and adhesive wear, when the film thickness lies between 72 and 123~nm.     

Effects of laser irradiation energy density on the properties of pulsed laser deposited ITO thin films

The properties of indium tin oxide (ITO) thin films, deposited at room temperature by simultaneous pulsed laser deposition (PLD), and laser irradiation of the substrate are reported. The films were fabricated from different Sn-doped In₂O₃ pellets at an oxygen pressure of 10 mTorr. During growth, a laser beam with an energy density of 0, 40 or 70 mJ/cm² was directed at the middle part of the substrate, covering an area of ∼1 cm². The non-irradiated (0 mJ/cm²) films were amorphous; films irradiated with 40 mJ/cm² exhibited microcrystalline phases; and polycrystalline ITO films with a strong 〈111〉> preferred orientation was obtained for a laser irradiation density of 70 mJ/cm². The resistivity, carrier density, and Hall mobility of the ITO films were strongly dependent on the Sn doping concentration and the laser irradiation energy density. The smallest resistivity of ∼1×10^-4 Ω cm was achieved for a 5 wt % Sn doped ITO films grown with a substrate irradiation energy density of 70 mJ/cm². The carrier mobility diminished with increasing Sn doping concentration. Theoretical models show that the decrease in mobility with increasing Sn concentration is due to the scattering of electrons in the films by ionized centers. PACS 81.15.Fg; 73.61.-r; 73.50.-h     

Phonon populations during pulsed laser annealing

A summary is presented of pulsed Raman and several other time-resolved experiments and the information they provide on the dynamics of electron-phonon and phonon-phonon interactions under pulsed laser annelaing (PLA) conditions. A number of recent cw Raman studies provide a much improved basis for understanding the consequences on Raman spectra of temperature-dependent resonance effects, high carrier density effects, phonon anharmonicity, and strain effects. New pulsed Raman studies, under PLA conditions, of the shift and shape of the first-order line and of the full first- and second-order spectra are discussed. Emphasis is placed on explaining the results of time-resolved Raman experiments in a framework consistent with other types of experiments. The Raman data appear to be compatible with the existence of a fluid phase followed by a hot solid near the normal melting point of Si. The data, however, indicate the presence of additional broadening of the first-order Raman line probably due to carrier-phonon interactions, and cooling rates which appear to be higher than predicted by thermal models.     

脉冲准分子激光淀积薄膜的实验研究

 利用两种脉宽(30ns，500fs)的KrF准分子激光展开了淀积类金刚石薄膜的实验研究，并且成功地制备了大面积不含氢成分的HF-DLC薄膜，运用时空分辨的等离子体发射光谱诊断系统和离子探针系统研究了等离子体特性对薄膜性能的影响。尝试了利用准分子激光制备非晶硅薄膜，研究了实验参数对非晶硅薄膜制备的影响，并分析了制备具有良好电学和光学性能的非晶硅薄膜的条件。     

XPS analysis and luminescence properties of thin films deposited by the pulsed laser deposition technique

This paper presents the effect of substrate temperature and oxygen partial pressure on the photoluminescence (PL) intensity of the Gd₂O₂S:Tb^3?+? thin films that were grown by using pulsed laser deposition (PLD). The PL intensity increased with an increase in the oxygen partial pressure and substrate temperature. The thin film deposited at an oxygen pressure of 900 mTorr and substrate temperature of 900°C was found to be the best in terms of the PL intensity of the Gd₂O₂S:Tb^3?+? emission. The main emission peak due to the ⁵D₄–⁷F₅ transition of Tb was measured at a wavelength of 545 nm. The stability of these thin films under prolonged electron bombardment was tested with a combination of techniques such as X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and Cathodoluminescence (CL) spectroscopy. It was shown that the main reason for the degradation in luminescence intensity under electron bombardment is the formation of a non-luminescent Gd₂O₃ layer, with small amounts of Gd₂S₃, on the surface.     

Nanostructured silver thin films deposited by pulsed laser ablation

Nanostructured thin films were deposited by excimer laser ablation of silver targets in controlled atmospheres of He and Ar. The film structural properties were investigated by means of scanning electron microscope and transmission electron microscope imaging. The film growth mechanism was identified as the result of coalescence of nanometric clusters formed during plume flight. Cluster formation involves plume confinement as a consequence of the increased collisional rate among plasma species. Fast photography imaging of the laser-generated silver plasma allowed to identify plasma confinement, shock wave formation and plasma stopping.     

Electrical properties of boron-doped diamond-like carbon thin films deposited by femtosecond pulsed laser ablation

We report on electrical measurements and structural characterization performed on boron-doped diamond-like carbon thin films deposited by femtosecond pulsed laser deposition. The resistance has been measured between 77 and 300 K using four probe technique on platinum contacts for different boron doping. Different behaviours of the resistance versus temperature have been evidenced between pure DLC and boron-doped DLC. The a-C:B thin film resistances exhibit Mott variable range hopping signature with temperature. Potential applications of DLC thin films to highly sensitive resistive thermometry is going to be discussed.     

激光烧蚀溅射沉积薄膜的研究现状

激光烧蚀溅射沉积薄膜技术是一项新的固体薄膜制造技术.文内简单地介绍了这项技术产生的历史背景、进化过程;根据相关文献,详细描述了这项技术的原理;基于最新资料,全面讨论了这项技术的国内外研究现状;总结了该技术的优、缺点;客观评价了该技术的应用前景和研究意义;并对该技术的今后研究方向提出了建议.     

Influence of oxygen partial pressure on the properties of pulsed laser deposited nanocrystalline zirconia thin films

ZrO₂ thin films were deposited at various oxygen partial pressures (2.0 × 10⁻⁵-3.5 × 10⁻¹ mbar) at 973 K on (1 0 0) silicon and quartz substrates by pulsed laser deposition. The influence of oxygen partial pressure on structure, surface morphology and optical properties of the films were investigated. X-ray diffraction results indicated that the films are polycrystalline containing both monoclinic and tetragonal phases. The films prepared in the oxygen partial pressures range 2.0 × 10⁻⁵-3.5 × 10⁻¹ mbar contain nanocrystals of sizes in the range 54-31 nm for tetragonal phase. The peak intensity of the tetragonal phase decreases with the increase of oxygen partial pressures. Surface morphology of the films examined by AFM shows the formation of nanostructures. The RMS surface roughness of the film prepared at 2.0 × 10⁻⁵ mbar is 1.3 nm while it is 3.2 nm at 3.5 × 10⁻¹ mbar. The optical properties of the films were investigated using UV-visible spectroscopy technique in the wavelength range of 200-800 nm. The refractive index is found to decrease from 2.26 to 1.87 as the oxygen partial pressure increases from 2.0 × 10⁻⁵ to 3.5 × 10⁻¹ mbar. The optical studies show two different absorption edges corresponding to monoclinic and tetragonal phases.     

Characterization of zirconium thin films deposited by pulsed laser deposition

Zirconium(Zr) thin films deposited on Si(100) by pulsed laser deposition(PLD) at different pulse repetition rates are investigated. The deposited Zr films exhibit a polycrystalline structure, and the X-ray diffraction(XRD) patterns of the films show the α Zr phase. Due to the morphology variation of the target and the laser–plasma interaction, the deposition rate significantly decreases from 0.0431 /pulse at 2 Hz to 0.0189 /pulse at 20 Hz. The presence of droplets on the surface of the deposited film, which is one of the main disadvantages of the PLD, is observed at various pulse repetition rates. Statistical results show that the dimension and the density of the droplets increase with an increasing pulse repetition rate. We find that the source of droplets is the liquid layer formed under the target surface. The dense nanoparticles covered on the film surface are observed through atomic force microscopy(AFM). The root mean square(RMS) roughness caused by valleys and islands on the film surface initially increases and then decreases with the increasing pulse repetition rate.The results of our investigation will be useful to optimize the synthesis conditions of the Zr films.     

Growth and characterization of pulsed laser deposited ZnO thin films

One of the most important and promising materials from metal oxides is ZnO with specific properties for near UV emission and absorption optical devices. The properties of ZnO thin films strongly depend on the deposition method. Among them, pulsed laser deposition (PLD) plays an important role for preparing various kinds of ZnO films, e.g. doped, undoped, monocrystalline, and polycrystalline. Different approaches — ablation of sintered ZnO pellets or pure metallic Zn as target material are described. This contribution is comparing properties of ZnO thin films deposited from pure Zn target in oxygen atmosphere and those deposited from sintered ZnO target. There is a close connection between final thin film properties and PLD conditions. The surface properties of differently grown ZnO thin films are measured by secondary ion mass spectrometry (SIMS), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Furthermore, different approaches — ablation of sintered ZnO pellet or pure metallic Zn as target materials are described. The main results characterize typical properties of ZnO films versus technological parameters are presented. Presented at 5-th International Conference Solid State Surfaces and Interfaces, November 19–24, 2006, Smolenice Castle, Slovakia     

Silicon epitaxy by pulsed laser annealing of evaporated amorphous films

Epitaxial growth of amorphous silicon layers deposited on Si-(100) substrates at room-temperature has been achieved by irradiation with very short laser pulses, as was evidenced from Rutherford backscattering analysis in combination with the channeling effect technique.     

Physical investigations on pulsed laser deposited nanocrystalline ZnO thin films

The nanocrystalline ZnO thin films were deposited by pulsed laser deposition on quartz and i-Si (100) substrates at different substrate temperatures (473 K–873 K) and at different mixed partial pressures (0.05, 0.01, and 0.5 mbar) of Ar+O₂. The structural studies from XRD spectra reveals that the films deposited at 0.05 mbar and at lower substrate temperatures were c-axis oriented with predominant (002) crystallographic orientation. At 873 K along with (002) orientation, additional crystallographic orientations were also observed in case of films deposited at 0.01 and 0.5 mbar pressures. The composition of Zinc and Oxygen in ZnO films from EDAX reveals that the films deposited at lower partial pressures were have high at.% of O₂ whereas higher partial pressures and substrate temperatures had high at.% Zn. The surface microstructure of the films show that the films deposited at lower partial pressures (0.05 mbar ) and at lower substrate temperatures (473 K) were found to have nanoparticles of size 15 nm where as films deposited at 873 K have nanorods. The length of these nanorods increases with increasing Ar+O₂ partial pressure to 0.5 mbar. The optical energy gap of the film deposited at lower partial pressure and substrate temperature was 3.3 eV and decrease with the increase of substrate temperatures. The films deposited at 0.5 mbar and at 873 K emitted an intense luminescence at a wavelength of 390 nm. The measured thickness of deposited films by spectroscopic ellipsometry is around 456 nm.