Defect formation in hafnium dioxide thin films

Hafnium dioxide thin films were deposited by reactive electron-beam evaporation at six different substrate temperatures on fused-silica substrates. During the depositions, the scattering of light caused by the growth of defects in the films was recorded with in situ total internal reflection microscopy. After deposition the films were analyzed by angle-resolved scatterometery, spectrophotometric measurement of film reflectance and transmittance, atomic force microscopy, and x-ray diffraction. We explore the effects of film defect formation on film optical properties and film surface topography using these data.     

Laser-deposited tin dioxide and tin acetylacetonate layers for gas sensors

Thin active layers were deposited by the pulsed laser deposition (PLD) method from tin dioxide and tin acetylacetonate targets. The deposition was carried out employing an excimer KrF laser. The structure and parameters of the deposited layers were studied in connection with gas sensor applications. The influence of Ni dopant and Pd catalyst was investigated, employing PLD technology in order to introduce dopants as a multilayered structure. The properties of these layers were studied by Fourier transform infrared (FTIR), and X-ray photoelectron (XPS) spectroscopies and by measurement of their d.c. resistance. Under reducing gases the resistance of Ni-doped tin dioxide with a Pd catalyst layer decreases by 3 orders and the resistance of tin acetylacetonate with a Pd catalyst by 2 orders (synthetic air versus 1000 ppm H₂. Due to this, such layers are suitable as the active layers of gas sensors.     

Development of crystallinity and morphology in hafnium dioxide thin films grown by atomic layer epitaxy

The structural development of HfO₂ thin films grown from HfCl₄ and water onto glass substrates by atomic layer epitaxy at 500 °C was studied with X-ray diffraction, atomic force microscopy and scanning electron microscopy. The films were found to contain two regions of different crystallinity: a thin amorphous starting layer and a subsequent preferentially oriented polycrystalline layer. The films were built up of densely packed grains. Substantial surface roughening occurred along with increasing film thickness. The films were chlorine free as analyzed by Rutherford backscattering spectrometry.     

Evaluation of hafnium nitride thin films sputtered from a hafnium nitride target

Hafnium nitride (HfN) thin films were prepared on Si (100) substrates by radio frequency magnetron sputtering with a compound target. Nitrogen composition, work function and electrical resistivity were investigated to evaluate thin film properties. Nitrogen composition and work function had little dependence on argon gas pressure and radio frequency power. Electrical resistivity showed strong correlation with the substrate temperature. When thin films were fabricated at room temperature, the electrical resistivity was 100 μΩ cm, and it became lower with an increase in the substrate temperature. When the films were fabricated at 600 °C, the resistivity became less than 50 μΩ cm.     

Silicon dioxide and hafnium dioxide evaporation characteristics from a high-frequency sweep e-beam system

Reactive oxygen evaporation characteristics were determined as a function of the front-panel control parameters provided by a programmable, high-frequency sweep e-beam system. An experimental design strategy used deposition rate, beam speed, pattern, azimuthal rotation speed, and dwell time as the variables. The optimal settings for obtaining a broad thickness distribution, efficient silicon dioxide boule consumption, and minimal hafnium dioxide defect density were generated. The experimental design analysis showed the compromises involved with evaporating these oxides.     

Effect of ion bombardment on thin hafnium nitride films

The use of ion bombardment in the modification of the surface mechanical properties of hafnium nitride has been investigated. Initially the deposition rate and the composition of the films prepared under different conditions of bias potential, partial pressure of N₂ and substrate temperature during r.f. sputtering were analyzed by Rutherford backscattering spectrometry and ¹⁴N(d, ∝)¹²C nuclear reaction. The concentration of hafnium in the film was dependent on both the substrate temperature and the partial pressure of N₂ during sputtering. Films bombarded with 500 keV Kr⁺ ions at different doses (10¹⁵-10¹⁷ ions cm^-2) indicate only moderate changes in the microhardness compared with similar studies of TiN films. However, the HfN films showed a greater improvement in adhesion compared with TiN films at lower ion doses. Ion channeling studies on single-crystal stainless steel substrates did not show any evidence of ion-induced mixing or recoil implantation of hafnium into the substrate. Preliminary measurements of the sputtering yield at high energies indicate that the modifications in microhardness and adhesion of the films may be explained by possible recoil implantation of some nitrogen into the substrate.     

Electron-microscopic study of Sn-chrisotile asbestos nanocomposite

Transmission electron microscopy was used to study the structural state of tin in Sn-chrisotile asbestos nanocomposite. It is shown that tin in the nanocomposite forms a system of nanowires, which, in turn, consist of crystallites of different lengths. Various orientational relations between the matrix and crystallites are revealed.     

二氧化钛薄膜材料的制备及其性能研究

采用溶胶-凝胶法,以钛酸丁酯[Ti(OC4O9)]4为原料,乙醇为溶剂,冰醋酸为抑制剂,制备了二氧化钛薄膜,同时以硝酸镧和硝酸镍为掺杂物制备了单掺、共掺的二氧化钛薄膜,研究了其可见光吸收性能和光催化降解性能。实验表明,掺杂后的二氧化钛薄膜在可见光区仍有明显吸收,掺镧的二氧化钛薄膜对亚甲基蓝降解效果较好,光催化降解率达到76.54%。     

Electrical and optical properties of nanocrystalline yttrium-doped hafnium oxide thin films

Yttrium-doped hafnium oxide (YDH) films have been produced by sputter-deposition by varying the growth temperature (T_s) from room-temperature (RT) to 400 °C. The electrical and optical properties of YDH films have been investigated. Structural studies indicate that YDH films grown at T_s = RT − 200 °C were amorphous and those grown at 300-400 °C are nanocrystalline. The crystalline YDH films exhibit the high temperature cubic phase of HfO₂. Spectrophotometry analysis indicates that all the YDH films are transparent. The band gap of YDH films was found to be in the range of 6.20-6.28 eV. Frequency variation of frequency dependent resistivity indicates the hopping conduction mechanism operative in YDH films. While the electrical resistivity (ρ_ac) is ~ 1 Ω-m at low frequencies (100 Hz), ρ_ac decreases to ~ 10^− 4 Ω-cm at higher frequencies (1 MHz).     

Electron-microscopic study of the polyimide-C70 fullerene system

The structure of a polyimide-C₇₀ fullerene system was studied on an HU-11B electron microscope at an accelerating voltage of 75 kV. The formation of a conjugated organic system representing a polyimide matrix sensitized by fullerenes was traced.     

C、Hf薄膜抑制栅极电子发射的机理研究

利用双离子束溅射和射频磁控溅射技术在Mo基底上分别制备了C膜和Hf膜,并利用化学方法制备了BaO涂层以模拟行波管栅极结构,随后在N2保护下,通过在900～1300K范围内退火,研究样品处于高温工作环境下表面相结构和成分的变化,以此解释了C、Hf薄膜抑制栅极电子发射的工作机理.     

C、Hf薄膜抑制栅极电子发射的机理研究

利用双离子束溅射和射频磁控溅射技术在Mo基底上分别制备了C膜和Hf膜，并利用化学方法制备了BaO涂层以模拟行波管栅极结构．随后在N2保护下．通过在900～1300K范围内退火．研究样品处于高温工作环境下表面相结构和成分的变化．以此解释了C、Hf薄膜抑制栅极电子发射的工作机理。     

Influence of hydrogen annealing on the properties of hafnium oxide thin films

Thin films of hafnium oxide were deposited by electron beam evaporation, and were subsequently annealed in hydrogen. X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy, photoluminescence, spectrophotometry, and current–voltage measurements were performed to investigate the structural, chemical, optical, and electrical properties of the films. As-deposited films were amorphous and nearly stoichiometric. Annealing led to crystallization of the films, and reduction of stoichiometry. Photoluminescence measurements revealed the presence of oxygen-related defects. Optically, the films were transparent with a wide band gap, and this was not affected by hydrogen annealing. Moreover, the films were suitable as anti-reflection coatings on silicon. The electrical resistivity of the films was significantly reduced as a result of annealing.     

Effects of substrate temperatures on the structure and properties of hafnium dioxide films

Different HfO2 monolayers under different deposition conditions, such as substrate temperature and oxygen partial pressure, were prepared from metal hafnium using the reactive electron beam evaporation method. X-ray diffraction was applied to determine the crystalline phase of these films, the surface morphology of the samples was examined by atomic force microscopy, and the optical properties were analyzed using a spectrophotometer and the surface thermal lens technique. The relationship between substrate temperature and film characteristic was investigated, and the correlation between the observed film properties and the laser damage threshold was also discussed.     

Optical properties of hafnium oxide thin films and their application in energy-efficient windows

Thin films of hafnium oxide were deposited by electron beam evaporation. The films were characterized using X-ray diffraction, X-ray photoelectron spectroscopy and normal incidence transmittance. The films were amorphous, stoichiometric, and transparent down to a wavelength of 300 nm. The optical properties of the films, including the refractive index, the absorption index and the bandgap, were determined. The refractive index, in the visible, was relatively high (1.89). The direct bandgap was found to be 5.41 eV. Absorption was insignificant for wavelengths above 250 nm. A heat mirror was built based on the hafnium oxide/silver/hafnium oxide/glass system. This heat mirror was found to be transparent in the visible with an average transmittance of 72.4%, and reflective in the near infrared (wavelength = 700–2000 nm) with an average reflectance of 67.0%. Such a heat mirror can be used in applications involving energy-efficient windows.     

Electron-microscopic study of grain-size distribution function in splat-cooled aluminium

The one-dimensional grain-size distribution function in splat-cooled aluminium samples and its dependence on sample storage conditions (temperature and time) were determined by electron microscopy. In contrast to previously published results [1], the theoretical logarithmic normal distribution function gave a very good representation of the experimental data obtained in this work. In addition, some aspects of quenching efficiency and reproducibility of the results for the two-piston splat-cooling device are discussed.     

Conformal growth and characterization of hafnium silicate thin film by MOCVD using HTB (hafnium tertra-tert-butoxide) and TDEAS (tetrakis-diethylamino silane)

Hafnium silicate (HfSi _x O _y ) films were deposited by metal-organic chemical vapor deposition (MOCVD) using hafnium tetra-tert-butoxide [HTB, Hf(OC(CH₃)₃)₄] and tetrakis-diethylamino silane [TDEAS, Si(N(C₂H₅)₂)₄]. The grown Hf-silicate films showed Hf-rich composition and impurity concentrations less than 1 atomic % (below detection limits). Uniformly deposited films with good step-coverage were obtained on hole-patterned SiO₂ substrates. Hafnium silicate films had stable amorphous crystalline structure up to 800 °C annealing and above 900 °C, a tetragonal HfO₂ crystal phase was observed. Dielectric constant (k) of the Hf-silicate films was about 15 and flat band voltage (V _fb) and hysteresis were very low.     

Compositional analysis of polycrystalline hafnium oxide thin films by heavy-ion elastic recoil detection analysis

The composition of polycrystalline hafnium oxide thin films has been measured by heavy-ion elastic recoil detection analysis (HI-ERDA). The films were deposited by high-pressure reactive sputtering (HPRS) on silicon wafers using an oxygen plasma at pressures between 0.8 and 1.6 mbar and during deposition times between 0.5 and 3.0 h. Hydrogen was found to be the main impurity and its concentration increased with deposition pressure. The composition was always slightly oxygen-rich, which is attributed to the oxygen plasma. Additionally, an interfacial silicon oxide thin layer was detected and taken into account. The thickness of the hafnium oxide film was found to increase linearly with deposition time and to decrease exponentially with deposition pressure, whereas the thickness of the silicon oxide interfacial layer has a minimum as a function of pressure at around 1.2 mbar and increases slightly as a function of time. The measurements confirmed that this interfacial layer is formed mainly during the early stages of the deposition process.