Properties of permalloy films produced in low-temperature plasma flows with a controlled composition

A simple version of a flow-forming plasma sputtering system is proposed. The causes that determine the properties of the deposited films are revealed when the composition, energy, and particle density of the flow are controlled. The electron component of the plasma flow and an increase in its ion component are found to degrade the magnetic properties of the films. The ferromagnetic resonance (FMR) line half-width of 10- to 150-nm-thick films is shown to mainly depend on the energy of the neutral flow component, which is specified by the sputtering conditions at an anode voltage of 400–700 V. In this rather narrow energy range, the FMR line half-width is 25 Oe for cold substrates.     

Structural, optical and electrical properties of tin oxide thin film deposited by APCVD method

Tin oxide (SnO₂) thin films have been grown on glass substrates using atmospheric pressure chemical vapour deposition (APCVD) method. During the deposition, the substrate temperature was kept at 400°C–500°C. The structural properties, surface morphology and chemical composition of the deposited film were studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and Rutherford back scattering (RBS) spectrum. XRD pattern showed that the preferred orientation was (110) having tetragonal structure. The optical properties of the films were studied by measuring the transmittance, absorbance and reflectance spectra between λ = 254 nm to 1400 nm and the optical constants were calculated. Typical SnO₂ film transmits ∼ 94% of visible light. The electrical properties of the films were studied using four-probe method and Hall-voltage measurement experiment. The films showed room temperature conductivity in the range 1.08 × 10² to 1.69 × 10² Ω⁻¹cm⁻¹.     

On the properties and stability of thermally evaporated Ge–As–Se thin films

Thin films of Ge–As–Se chalcogenide glasses have been deposited by thermal evaporation from bulk material and submitted to thermal treatments. The linear refractive index and optical band-gap for as-deposited and annealed films have been analyzed as function of the deposition parameters, chemical composition and mean coordination number (MCN). The chemical composition of the films was found to be directly affected by deposition rate, with low rates producing films with elevated Ge and reduced As content, whilst at high rates the Ge content was generally reduced and As levels increased compared with the bulk starting material. As a result films with close to the same stoichiometry as the bulk glass could be obtained by choosing appropriate deposition conditions. As-deposited films with MCN in between 2.44 and 2.55 showed refractive indices and optical band-gaps very close to those of the bulk glass whereas outside this range the film indices were higher and the optical gaps lower than those of the bulk glass. Upon annealing at close to their glass transition temperature, high MCN films evolved such that their indices and band-gaps approached the bulk glass values whereas at low MCN films resulted in no changes to the film properties.     

Structural,optical and electrical properties of post annealed Mg doped ZnO films for optoelectronics applications

Mg _x Zn_1-x O films with 0.15 mole composition of Magnesium were successfully deposited by the spin coating sol–gel method. Zinc acetate dihydrate and Magnesium acetate were used as starting precursors to prepare the solution in ethanol solvent. The MgZnO films were deposited on microscopic glass substrates and post annealed at three different temperatures. X-ray Diffractometer (XRD), Scanning Electron Microscopy (SEM) and UV–VIS Spectrophotometer were used to characterize the deposited films for studying structural and optical properties. Energy dispersive analysis by X-ray (EDAX) was used to determine incorporation of Mg content in ZnO films. XRD spectrum reveals that, the deposited Mg doped ZnO films were polycrystalline in nature. The intensity of c-axis in the XRD spectrum goes on decreasing as Mg composition slightly increasing corresponding to increase in annealing temperature. EDAX spectra clearly showed the incorporation of Mg into the ZnO films. Semiconductor characterization system was used for the I–V characterization of MgZnO films. I–V characteristics show decrease in current as increase in the biased voltage. Optical band gap of MgZnO films was found to be increased from 3.2 to 3.38 eV as estimated from the absorption coefficients.     

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     

Hybrid ICP/sputter deposition of TiC/CaO nanocomposite films for biomedical application

TiC/a-C nanocomposite films doped with CaO have been deposited by means of a hybrid PVD/PACVD technique, which combines dc magnetron sputtering of a TiC_0.5+10% CaO target, with a subsequent high density inductively coupled plasma (ICP) in order to excite and ionize the sputtered species to a high degree. The films were characterized according to their morphology, structure and thickness by scanning electron microscopy, their composition and bonding structure by X-ray photoelectron spectroscopy, and their crystalline properties by X-ray diffraction. The films consist of fcc titanium carbide nanocrystallites with grain sizes of 5–15 nm and an amorphous carbon phase. The average composition is Ti_0.43C_0.35Ca_0.02O_0.15N_0.05. The influence of the ICP plasma power and the bias voltage applied to the substrate on the major film properties has been investigated. A number of such TiC/a-C/CaO nanocomposite films on silicon substrates have been subjected to a 60 day cell test with human osteoblastic cells in order to investigate their suitability for the coating of prostetic implants. The results of these cell tests, some of which turned out to be rather promising, are discussed in terms of film properties such as surface roughness and biaxial stress. PACS 68.55.-a; 81.07.-b; 87.68.+z     

Influence of the plasma parameters on the properties of aluminum oxide thin films deposited by laser ablation

The plasma produced by the ablation of a high purity Al₂O₃ target, using the fundamental line (1064 nm) of a Nd:YAG laser, was characterized. The laser fluence was varied in order to study its effect on the characteristics of the produced plasma as well as on the properties of the material deposited. Optical emission spectroscopy (OES) was used to determine the type of excited species present in the plasma. The mean kinetic energy of the ions and the maximum plasma density were determined from the time of flight (TOF) curves, obtained with a planar Langmuir probe. The obtained results reveal that the fast peak in the probe curve could be attributed to Al III, while the slow peak corresponds to the Al II. Aluminum oxide thin films were then deposited under the same conditions of the diagnosed plasma, in an attempt to correlate the plasma parameters with the properties of the deposited material. It was found that when Al II ion energies are lower than 461.0 eV the films deposited have structural characteristics similar to that of α-Al₂O₃, whereas at ion energies greater than 461.0 eV amorphous material was obtained.     

Electrical properties of simultaneously evaporated Sb-Te thin films

Thin films of Sb-Te of varying compositions have been deposited on glass substrates following the three temperature method. The dc conductivity (σ), Hall coefficient (R _H) and thermoelectric power (α) of annealed samples have been measured in the temperature range 300–470°K. Films exhibit metallic as well as semiconducting characteristics withp-type conductivity. The properties are found to be dependent on composition and thickness of the film. Paper presented at the Int. Conf. and Intensive Tutorial Course on Semiconductor Materials, New Delhi, India, December 8–16, 1988.     

Microstructural study of thin films of 5 mol% gadolinia doped ceria prepared by pulsed laser ablation

Microstructural characterization of thin films of 5 mol% gadolinia doped ceria films deposited by pulsed laser ablation in the energy range 100–600 mJ/pulse has been investigated, as deposited films were found to be nanocrystalline with preferred orientation. X-ray diffraction analysis revealed that the size of the nanocrystals of doped ceria does not vary significantly with increasing laser energy, whereas transmission electron microscopy study showed a uniform distribution of nanocrystal of 8–10 nm for energies ≤200 mJ/pulse and nanocrystals embedded in a large crystalline matrix of doped ceria for energies in the range 400–600 mJ/pulse. Although the laser-ablated films were totally free from secondary phases, lattice imaging of the large grained doped ceria showed growth-induced defects, such as dislocations and ledges.     

Low-macroscopic field emission from nanocrystalline Al doped SnO<Subscript>2</Subscript> thin films synthesized by sol–gel technique

We have observed low-macroscopic field electron emission from wide bandgap nanocrystalline Al doped SnO₂ thin films deposited on glass substrates. The emission properties have been studied for different anode-sample spacings and for different Al concentrations in the films. The turn-on field and approximate work function were calculated and we have tried to explain the emission mechanism from this. The turn-on field was found to vary in the range 5.6–7.5 V/μm for a variation of anode sample spacing from 80–120 μm. The turn-on field was also found to vary from 4.6–5.68 V/μm for a fixed anode-sample separation of 80 μm with a variation of Al concentration in the films 8.16–2.31%. The Al concentrations in the films have been measured by energy dispersive X-ray analysis. Optical transmittance measurement of the films showed a high transparency with a direct bandgap ∼3.98 eV. Due to the wide bandgap, the electron affinity of the film decreased. This, along with the nanocrystalline nature of the films, enhanced the field emission properties. PACS 81.20.Fw; 61.10.-i; 79.70.+q     

Laser ablation of La0.9Sr0.1Ga0·8Mg0.2O2.85 — plume and film characterization

Thin films of La_0.9Sr_0.1Ga_0·8Mg_0.2O_2.85 (LSGMO), an electrolyte material for the solid oxide fuel cells (SOFC), have been prepared by pulsed laser deposition method. Preparation of thin films under high vacuum gives amorphous films, which on annealing at 730 °C in air give stochiometric thin films. Highly oriented, polycrystalline and amorphous films of LSGMO are obtained on SrTiO₃ (001), sapphire (0001) and quartz substrates, respectively. The ionic conductivity value for the film deposited on sapphire substrate is an order of magnitude larger than for the film deposited on SrTiO₃. The plume composition is analyzed by a mass spectrometer. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

Synthesis of nanometric iron oxide films by RPLD and LCVD for thermo–photo sensors

Iron oxide films were deposited on <100> Si substrates by reactive pulsed laser deposition (RPLD) using a KrF laser (248 nm). These films were deposited too by laser (light) chemical vapor deposition (LCVD) using continuous ultraviolet photodiode radiation (360 nm). The deposited films demonstrated semiconducting properties. These films had large thermo-electromotive force (e.m.f.) coefficient (S) and high photosensitivity (F). For films deposited by RPLD the S coefficient varied in the range 0.8–1.65 mV/K at 205–322 K. This coefficient depended on the band gap (E _g ) of the semiconductor films, which varied in the range 0.43–0.93 eV. The largest F value found was 44 V_c/W for white light at power density I≅0.006 W/cm². Using LCVD, iron oxide films were deposited from iron carbonyl vapor. For these films, the S coefficient varied in the range −0.5 to 1.5 mV/K at 110–330 K. The S coefficient depended on E _g of the semiconductor films, which varied in the range 0.44–0.51 eV. The largest F value of these films was about 40 V_c/W at the same I≅0.006 W/cm². Our results showed that RPLD and LCVD can be used to synthesize iron oxide thin films with variable stoichiometry and, consequently, with different values of E _g . These films have large S coefficient and high photosensitivity F and therefore can be used as multi-parameter sensors: thermo–photo sensors.     

Carbon nanotubes as nanoparticles collector

This communication reports on a new method for the collection of nanoparticles using carbon nanotubes (CNT) as collecting surfaces, by which the problem of agglomeration of nanoparticles can be circumvented. CNT (10–50 nm in diameter, 1–10 μm in length) were grown by thermal CVD at 923 K in a 7 v/v% C₂H₂ in N₂ mixture on electroless nickel-plated copper transmission electron microscopy (TEM) grids and Monel coupons. These samples were then placed downstream of an arc plasma reactor to collect individual copper nanoparticles (5–30 nm in diameter). It was observed that the Cu nanoparticles preferentially adhere onto CNT and that the macro-particles (diameter >1 μm), a usual co-product obtained with metal nanoparticles in the arc plasma synthesis, are not collected. Cu–Ni nanoparticles, a catalyst for CNT growth, were deposited on CNT to grow multibranched CNT. CNT-embedded thin films were produced by re-melting the deposited nanoparticles.     

Optical and structural analysis of plasma-treated and annealed Al–Sb bilayer thin films

Aluminum–antimony (Al–Sb) seems to be a promising semiconducting material for high-temperature application especially for transistors and P–N junction diodes and is a highly coefficient solar material. No attempt has been made to study the bilayer diffusion properties of Al–Sb thin film by plasma exposure. In this paper, the characterization of plasma-exposed Al–Sb bilayer thin films is presented. Thin films were coated by thermal vapor coating technique, and after coating, the sample was annealed and exposed with plasma. Results were obtained from optical band gap data and X-ray diffraction for treated and untreated Al–Sb thin films, and these results were compared with annealed Al–Sb thin films.     

Nano-ionic thin films of gadolinia-doped ceria prepared by pulsed laser ablation

Microstructural properties of nano-ionic thin films of gadolinia-doped ceria (GDC) prepared by pulsed laser ablation from sintered targets of gadolinia (5–20 mol%) doped ceria are investigated. The ionic conductivity measurements of the sintered pellets showed a decrease in the activation energy from 1.1 to 0.65 eV for 5 and 30 mol% gadolinia-doped ceria, respectively. The microstructural properties of the GDC films as a function of substrate temperature, oxygen partial pressure, and laser energy show that the films are polycrystalline in the entire range of substrate temperature. The grain size is found to increase with increasing temperature up to 873 K. Further improved crystallinity is noticed for the films grown with oxygen partial pressure of 0.1–0.2 mbar. X-ray diffraction and transmission electron microscopy (TEM) reveal nanocrystalline grains with textured growth along <111> orientation in these films at low substrate temperature and at lower oxygen partial pressure. TEM study shows a uniform distribution of nanocrystal of 8–10 nm for energies ≤200 mJ/pulse, and nanocrystals embedded in a large crystalline matrix of doped ceria for energies in the range 400–600 mJ/pulse. Raman spectroscopy also confirms the defects in these films. The study also reveals that the substrate temperature and oxygen partial pressure could influence preferred orientation, while the laser energy could significantly influence defect concentration in these films. Invited paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006.     

Development of conductive transparent indium tin oxide (ITO) thin films deposited by direct current (DC) magnetron sputtering for photon-STM applications

Highly conductive and transparent indium tin oxide (ITO) thin films, each with a thickness of 100 nm, were deposited on glass and Si(100) by direct current (DC) magnetron sputtering under an argon (Ar) atmosphere using an ITO target composed of 95% indium oxide and 5% tin oxide for photon-STM use. X-ray diffraction, STM observations, resistivity and transmission measurements were carried out to study the formation of the films at substrate temperatures between 40 and 400 °C and the effects of thermal annealing in air between 200 and 400 °C for between1 and 5 h. The film properties were highly dependent on deposition conditions and on post-deposition film treatment. The films deposited under an Ar atmosphere pressure of ∼1.7×10^-3 Torr by DC power sputtering (100 W) at substrate temperatures between 40 and 400 °C exhibited resistivities in the range 3.0–5.7×10^-5 Ω m and transmissions in the range 71–79%. After deposition and annealing in air at 300 °C for 1 h, the films showed resistivities in the range 2.9–4.0×10^-5 Ω m and transmissions in the range 78–81%. Resistivity and transmission measurements showed that in order to improve conductive and transparent properties, 2 h annealing in air at 300 °C was necessary. X-ray diffraction data supported the experimental measurements of resistivity and transmission on the studies of annealing time. The surface roughness and film uniformity improve with increasing substrate temperature. STM observations found the ITO films deposited at a substrate temperature of 325 °C, and up to 400 °C, had domains with crystalline structures. After deposition and annealing in air at 300 °C for 1 h the films still exhibited similar domains. However, after deposition at substrate temperatures from 40 °C to 300 °C, and annealing in air at 300 °C for 1 h, the films were shown to be amorphous. More importantly, the STM studies found that the ITO film surfaces were most likely to break after deposition at a substrate temperature of 325 °C and annealing in air at 300 °C for 2 or 3 h. Such findings give some inspiration to us in interpreting the effects of annealing on the improvement of conductive and transparent properties and on the transition of phases. In addition, correlations between the conductive/transparent properties and the phase transition, the annealing time and the phase transition, and the conductive/transparent properties and the annealing time have been investigated. Received: 10 July 2000 / Accepted: 27 October 2000 / Published online: 9 February 2001     

NIR photoresponse in the mixed phthalocyanine films

The structure, optical and conducting properties of thin vacuum deposited films of erbium bisphthalocyanine (Pc₂Er) and its mixtures with metal-free phthalocyanine (H₂Pc) have been studied with particular reference to the near infrared (NIR). It has been found that, in spite of intense optical absorbance over the UV/Vis/NIR domain, pure Pc₂Er films are weakly photoconductive. However, in the mixed Pc₂Er/H₂Pc films the photocurrent signal was detected in the NIR range of 1200–1500 nm, which is associated with optical activity of Pc₂Er molecules. An erratum to this article is available at .     

CVD diamond films for electronics

Mechanical, optical, thermal and electronic properties of diamond films and chemical vapour deposition (CVD) techniques are briefly reviewed. Some spectroscopical methods for the characterization of CVD diamond films are described (optical absorption, photothermal deflection spectroscopy, Raman spectroscopy and electron paramagnetic resonance), together with our recent results on investigation of electronic properties of the main defects in this material, relevant to the application of CVD diamond films for the future electronic devices. Presented at the 6th Joint Seminar “Development of Materials Science in Research and Education”, Karlštejn, Czech Republic, 17–19 September 1996. This work was supported by Grant Agency of the Czech Republic, Grant No. 202/06/0446 and by the NATO Scientific Exchange Programme, HTECH.LG 940890 and NFWO (National Fonds voor Wetenschappelijk Orderzoek, Brussel) Project G.0014.96.     

Pulsed laser deposition of molybdenum oxide thin films

Thin films of molybdenum oxide were deposited in vacuum by pulsed laser ablation using a xenon fluoride (351 nm) and a krypton fluoride (248 nm) excimer lasers. The films were deposited on unheated substrates and were post-annealed in air in the temperature range 300–500°C. The structural, morphological, chemical, and optical properties of the films were studied. As-deposited films were found to be dark. The transparency of the films was improved with annealing in air. The films were polycrystalline with diffraction peaks that belong to the orthorhombic phase of MoO₃. The surface morphology of the films showed a layered structure. Both the grain size and surface roughness increased with annealing temperature. The stoichiometry of the films improved upon annealing in air, with the best stoichiometry of MoO_2.95 obtained for films deposited by the XeF laser and annealed at 400°C. Similarly, the best transparency, with a transmittance exceeding 80%, was obtained with the films annealed in the temperature range 400–450°C.     

The dynamics of accumulation of electrically active radiation defects on implantation of graded-band-gap HgCdTe films grown by MBE

The dynamics of accumulation of electrically active radiation defects under ion doping of epitaxial Cd _x Hg _1−x Te films is studied for various distributions of film composition in the implantation region. The epitaxial films were irradiated by boron ions at room temperature in the continuous regime, with the dose ranging within 10¹¹−3·10¹⁵ cm⁻², energy — 20–150 keV, and ion current density — j = 0.001–0.2 μA·cm⁻². It is found that the natural logarithm of the introduction rate of electrically active radiation defects linearly depends on the epitaxial-film composition in the range of mean projected path of implanted ions. An analysis of the experimental data shows that the dynamics of accumulation of electrically active radiation defects is determined by the epitaxial-film composition in the implantation region. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 25–28, September, 2006.