高温ITO薄膜应变计制备及压阻性能EI北大核心CSCD

高温薄膜应变计被广泛应用于极端条件热端构件的应变测量。ITO薄膜应变计通常能够应用于1000℃以上的应变测量,为了研究ITO薄膜的显微结构、XPS光谱、阻温特性及压阻响应,采用磁控溅射在陶瓷基底上制备了ITO薄膜应变计,并在高温纯N2中热处理ITO薄膜。结果表明,其电阻温度系数稳定在-750×10-6℃-1,在1200℃下测试其应变特性,测得电阻漂移率为0.0018 h-1,应变因子为16。ITO薄膜在高温下具有稳定的电阻温度系数和低漂移率,为高温端部件应变的测量提供了可能。     

Electrical,electromechanical and thermal properties of thin tellurium films

Thin films of tellurium of wide range of thicknesses have been deposited by vacuum evaporation and their electrical properties such as electrical resistivity and temperature coefficient of resistance have been measured. The suitability of these films for possible use as strain gauges has been studied and their strain resistivity behaviour is presented. The thermal conductivity of these films have been determined and these results are presented alongwith. An interesting phenomenon has been noticed. In all these effects an extraordinary behaviour is observed at a specific thickness. This smears out with an increase in the thickness of the film. These effects are explained in terms of size effects in thin films.     

The effect of ion bombardment on the strain gauge factor of thin gold films

Evaporated gold films of approximately 200 å in thickness have been bombarded with argon ions to increase the sheet resistance by sputter etching to a maximum of 40 kΩ/□. The strain gauge coefficient of resistance γ (i.e. the fractional change in resistance per unit strain) was measured for films with a wide range of sheet resistance, and was found to be almost invariant with an average value of 2.6. This contrasts greatly with the published values of γ of up to 100 for thin island-structure evaporated films of similar sheet resistance.The temperature coefficient β of the strain gauge factor was found to be similar in magnitude but opposite in sign to the temperature coefficient of resistance α, which was measured as + 12 × 10⁴ °C^-1.The measured values of γ, β and α agree well with the values calculated by assuming that the metallic conduction is modified by reduction of the electron mean free path. We therefore conclude that a connected metallic layer still exists even at very high values of sheet resistance.     

3.2 The electromechanical behaviour of a full component (dielectric and Cu/Ni constantan alloy) for thin film strain gauge deposited upon steel-substrate

We have elaborated and studied a full component (dielectric and Cu/Ni constantan alloy) in the form of thin film for use as a strain gauge on the strainable member of a pressure transducer. The dielectric layer is laid upon a steel substrate by successive evaporation of alumina and silicon monoxide. The alloy-film is deposited from separate sources by coevaporation, the nickel flux being monitored by the copper flux.The dielectric shows a fitting insulation resistance till 300°C and the alloy exhibits a resistance drift with temperature of less than 10^?4/°C. We observe a good mechanical endurance during a static strain-state of 3000 micro-deformations and during the course of a sinusoidal strain variation for more than 10⁶ cycles. The value of the gauge-factor is about 2.2.     

Effect of uniaxial stress on the electromechanical properties in ferroelectric thin films under combined loadings

The electromechanical properties of ferroelectric thin films under an alternating electric field and a static uniaxial compressive stress are investigated using the modified planar four-state Potts model. To implement the electromechanical properties and the coupling of the electrical and mechanical response, the mechanical energy density as well as the energy due to anisotropic switching between a-domain and c-domain are incorporated in the Hamiltonian. Besides, there are two contributions to the strain at each cell: eigenstrain and elastic strain. Our simulation results show that the longitudinal strain-electric field butterfly loop shifts downward along strain axis and that for the transverse strain shifts upward as the stress magnitude is increased. Moreover, the polarization-electric field hysteresis loop becomes a double-loop under a large compressive stress. The piezoelectric coefficient increases with the stress magnitude and reaches a maximum value at a critical stress level. It then gradually decreases to a small value at large stress magnitudes. Our results qualitatively agree with experimental ones.     

The magneto-optical properties of thin cobalt films

Experimentally measured magneto-optical properties of magnetic materials are usually analysed using a phenomenological approach in which the permittivity is considered as a skew-symmetric tensor. Measurements of the real and imaginary parts of both the optical and the magneto-optical elements of this sensor in the region 1.0–2.5 eV are presented for a series of seven thin (108-13.4 nm) cobalt films. The prominent features of the results are remarkably consistent from film to film.     

Adhesion and vacuum forming properties of tin-zinc thin films deposited on polyester film substrate

Sn-Zn alloy thin films were deposited on a polyester (PET) film substrate by co-evaporation and evaluated their surface, tensile and adhesion properties with a vacuum forming test and pull test.Relationship between the surface roughness and elemental composition of these thin films was evaluated. The surface roughness decreased with increase of the Sn content.The tensile property was estimated by observations of micro-cracks of the thin films due to a vacuum forming test. Sn-Zn alloy thin film, whose elemental composition is 85:15 (wt%), had high vacuum forming durability.The adhesion strength between the Sn-Zn alloy thin films and PET substrate was measured with a pull test apparatus. The pull strength decreased with increase of the Sn content.     

Effect of composition,film thickness and annealing on the optical properties of Bi-Sb-Se thin films

Thin films of Bi₁₀Sb _x Se_90–x (x35, 40, 45) of different composition and thickness, were deposited on glass substrates by vacuum evaporation. Optical absorption measurements show that the fundamental absorption edge is a function of glass composition, film thickness and annealing temperature. The optical absorption is due to indirect electronic transitions. The value of the optical band gap was found to increase with thickness and decreasing the antimony content and with increasing temperature of heat treatment. The validity of the Urbach rule was investigated and the respective parameters estimated. X-ray diffraction was used to obtain an insight into the structural information.     

A characterisation of thick film resistors for strain gauge applications

Some commercial thick film resistors with sheet resistivities from 1 kohm/sq. up to 1 Mohm/sq. were evaluated for strain gauge applications. Temperature coefficients of resistivity, noise indices and gauge factors (GFs) were measured. For the same resistor series GFs and noise indices increase with increasing sheet resistivity. However, both GFs and noise indices are different for resistors with the same nominal sheet resistivity but from different resistor series. The results indicated that the microstructure rather than the different chemical composition of the conductive phase in thick film resistors is the primary reason for the different gauge factors.     

Metal properties and thin film oxidation

The dependence of thin film oxidation rates on the metal properties is discussed in terms of a surface state charge at the metal-oxide interface and a space charge layer in the growing oxide. The properties considered are the magnetic change at the Curie temperature, allotropic transformation and crystal orientation of the metal substrate. Experimental data on the direct logarithmic oxidation of iron, nickel, cobalt and copper forming p-type semiconducting oxides are analysed.     

Preparation of strain-included rutile titanium oxide thin films and influence of the strain upon optical properties

Rutile type titanium dioxide (TiO₂) thin films are prepared by pulse laser deposition (PLD) with controlled oxygen pressure. Transmission electron microscopy (TEM) analysis clarified that crystalline structures, surface structures and electric states of the TiO₂ films almost correspond to those of the bulk rutile. We observed crystalline domain including strain in the PLD film. The strain of the TiO₂ film was measured by nano-beam diffraction. The strain-included domains affected properties of the film as optical absorption. The obtained optical band gap energy value was 3.30 eV, which was larger than that of bulk. TEM results such as crystalline grain sizes and distribution were used to consider quantum size effect in order to explain the larger band gap value. Moreover the influence of strain in rutile crystalline grains upon optical properties was suggested in the present study. The difference of band gap energy between experimental and theoretically calculated ones was considered to come from the strain effects.     

Role of the crystallinity of ZnO films in the electrical properties of bottom-gate thin film transistors

The strong correlation between the microstructural characteristics of ZnO channel layers grown at various temperatures by radio-frequency magnetron sputtering and the electrical performances of resulting bottom-gate thin film transistors (TFTs) was reported. Transmission electron microscopy revealed that increasing growth temperature enhanced degree of c-axis preferred orientation and enlarged width of columns in the ZnO films. The ZnO channel layers grown at 250 and 350 °C exhibited TFT saturation behavior. However, growing them at ≥ 350 °C produced small grains in the junctions of ZnO/SiO₂ interface and grain boundaries, which led to hump behavior in TFT transfer curve caused by formation of additional boundaries.     

The optical properties of zirconium diboride thin films

The optical properties of evaporated thin films of zirconium diboride were investigated from 4.1 to 11.3 eV. The optical constants were determined by reflectance measurements made at near-normal and oblique angles of incidence. The existence and energy of interband transitions and the plasma frequency are inferred from these results.     

The optical properties of sprayed CdS thin films

In the study presented in this paper we attempted to interpret the reflectance and the transmittance of sprayed CdS films. Assuming a model based on multilayer film theory we showed that sprayed CdS film is a combination of multilayer stacks of crystallites and gaseous inclusions.