Influence of thickness on H2 gas sensor properties in polycrystalline SnO x films prepared by ion-beam sputtering

Amorphous SnO _x films were deposited on sintered alumina substrates by ion-beam sputtering. They were annealed at 500° C for 2 h in air and polycrystalline films with thickness varying from about 1 to 700 nm were prepared. Film-sensor properties against 0.47% H₂ gas were measured as a function of thickness and the operating temperature for 150 to 350° C. The film thickness exhibiting a sensitivity maximum increased gradually with temperature. The optimum thickness shifted from 7 nm at 150° C to 175 nm at 350° C. Highly sensitive films lay in a narrow thickness range of 60 to 180 nm and films thinner or thicker than this were relatively insensitive at 300 and 350°C. A model was proposed to interpret the sensitivity behaviour in terms of thickness and grain-boundary effect.     

Thickness dependence of electrical properties in thin films of undoped indium oxide prepared by ion-beam sputtering

Preparation and electrical characterization of undoped indium oxide films were examined as a function of thickness and annealing. Thin films ranging from 1.1 to 113 nm thickness were deposited on glass substrates by ion-beam sputtering. Low-angle X-ray diffraction analysis in multi-layered films showed the possibility that physically continuous and almost flat films were formed even in the thinnest 1.1 nm films. Room temperature resistivity of as-deposited films decreased sharply by more than five orders of magnitude as the thickness increased from 1.1 to 5.2 nm. The 2.4 nm thick films, in its as-deposited state, showed a gradual resistivity modulation with the change of atmosphere between air and argon gas at room temperature. Annealing at 300° C for 5 h in air increased the resistivity drastically; the room temperature resistivity of 24.3 nm thick films changed from 2.2×10^–3 cm (as-deposited) to higher than 10⁵ cm (annealed).     

离子束溅射生长非晶Si薄膜的研究

用离子束溅射法制备了不同衬底温度的非晶硅(a-Si)薄膜,用双四探针法测量了不同温度下的电阻率,用喇曼散射及原子力显微镜表征了薄膜显微结构.结果发现随着衬底温度的升高,薄膜的电阻率逐渐增大,衬底温度为室温的a-Si薄膜质量较好且从其表面形貌可观察到少量Si晶粒的存在.     

Structural analysis of amorphous Si films prepared by magnetron sputtering

A study is presented on the structural changes occurring in thin amorphous silicon (a-Si) during thermal treatments. The a-Si films were deposited on single-crystalline Si substrates held at room temperature by magnetron sputtering of a Si target in pure Ar atmosphere, and therefore the films were hydrogen-free. All samples were annealed in vacuum and subsequently studied by electron paramagnetic resonance (EPR) and grazing incidence X-ray diffraction (GIXRD). A slight increase in the dangling bonds content at lower annealing temperatures, and then a strong increase of it at around 650 °C, suggested significant structural changes. The samples were also studied by grazing incidence small-angle X-ray scattering (GISAXS) which confirmed changes at the nanometric scale attributed to voids in the material. A nice correlation of the results of the three techniques shows advantages of this approach in the analysis of structural changes in a-Si material.     

Properties of indium oxide/tin oxide multilayered films prepared by ion-beam sputtering

The preparation and characterization of indium oxide (InO _x )/tin oxide (SnO _y ) multilayered films deposited by ion-beam sputtering are described and compared with indium tin oxide (ITO) films. The structure and the optoelectrical properties of the films are studied in relation to the layered structures and the post-deposition annealing. Low-angle X-ray diffraction analysis showed that most films retained the regular layered structures even after annealing at 500° C for 16 h. As an example, we obtained a resistivity of 6×10^–4 cm and a transparency of about 85% in the visible range at a thickness of 110 nm in a multilayered film of InO _x (2.0 nm)/SnO _y (0.2 nm)×50 pairs when annealed at 300° C for 0.5 h in air. Hall coefficient measurements showed that this film had a mobility of 17 cm² V^–1 sec^–1 and a carrier concentration (electron density) of 5×10²⁰ cm^–3.     

反应RF磁控溅射法制备非晶氧化硅薄膜及其特性研究

在氧气和氩气的混合气体中,在没有额外加热的条件下用反应射（RF）溅射硅靶制备了非晶氧化硅（a-SiO2)薄膜,并测试分析了薄膜的结构和电特性与O2／Ar流量比的关系。当固定氩气流量,改变氧气流量时,薄膜沉积速率先急剧减少,再增大,然后又减少。当O2／Ar≥0．075时,得到满足化学配比的氧化硅薄膜。并且,随着O2／Ar流量比的增大,薄膜的电阻,电场击穿强度都有所增大,而在HF缓冲溶液（BHF）中的腐蚀速率下降,所有的样品中无明显的H－OH水分子的红外吸收峰。比较发现反应射频（RF）磁控溅射法制备的a-SiO2薄膜具有良好的致密性和绝缘性。     

离子束溅射BST薄膜的制备及结构分析

本文采用离子束溅射的方法制备了不同衬底温度下的BST薄膜,用X射线、Raman、SPM等技术对晶体结构及微观形貌进行表征,研究了离子束溅射制备BST的工艺.     

Properties of Cu-doped ZnO films by RF sputtering method: Thickness dependence

We present results concerning the thickness dependence of structural, morphological and optical properties of the Zn_0.98Cu_0.02O films deposited on glass substrates using radio frequency (RF) sputtering method. The microstructure and the chemical state of oxygen, copper and zinc in ZnO and Zn_0.98Cu_0.02O films were investigated by X-ray diffraction spectroscopy (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The results indicate that Zn_0.98Cu_0.02O films are the wurtzite structure with strong c-axis orientation. Crystallinity of the films is closely related to the film thickness. With increasing film thickness, there are more surface (mainly nanopores) defects existing in the Zn_0.98Cu_0.02O films and surface roughness increases. XRD and XPS data show that the valence state of copper in the Zn_0.98Cu_0.02O films is Cu²⁺. The transparency of all films is more than 85% in the visible region.     

反应RF磁控溅射法制备非晶氧化硅薄膜及其特性研究

在氧气和氩气的混合气体中，在没有额外加热的条件下用反应射频（RF）溅射硅靶制备了非晶氧化硅(a-SiO     

Crystallization behaviour of amorphous SiC films prepared by r.f. sputtering

The crystallization behaviour of amorphous SiC (a-SiC) films prepared by r.f. diode sputtering was studied using IR measurements and transmission electron microscopy. The absorption band at around 800 cm^-1 in the IR spectrum became sharper and more intense when a sample was annealed above 1000°C, corresponding to the phase transition in the film from amorphous to polycrystalline β-SiC. From cross-sectional transmission electron microscopy observations, crystallization occured homogeneously in the film. The crystallization behaviour was independent of the film thickness and the substrate temperature during preparation. The measured overall activation energy of crystallization of a-SiC films is about 5.0 eV.     

采用粉末溅射的SnO2/CeO2薄膜气敏材料及元件

为改善气敏元件的性能 ,提高稳定性 ,采用粉末反溅研制了 SnO2/CeO2乙醇敏感材料 ,结果 表明灵敏度在 CeO2掺杂范围 4%- 32%、膜厚 100- 180nm时较佳 ,特征时间τ与膜厚 l遵循 τ∝ l2规律 ,研制出乙醇灵敏度 20- 80、特征时间 < 15s的微型平面旁热式 SnO2气敏元件 ;元件 灵敏度测试存在一个 4.5- 10.5V相对稳定的测试电压区间 ,且在湿度影响下显著降低.     

Thickness dependence of structure and optical properties of silver films deposited by magnetron sputtering

A series of silver films with different thickness were prepared under identical conditions by direct current magnetron sputtering. The optical properties of the silver films were measured using spectrophotometric techniques and the optical constants were calculated from reflection and transmission measurements made at near normal incidence. The results show that the optical properties and constants are affected by films' thickness. Below the critical thickness of 17 nm at which Ag film forms a continuous film, the optical properties and constants vary significantly as the thickness of films increases and then tends to a stable value which is reached at 41 nm. X-ray diffraction measurements were carried out to examine the structure and stress evolution of the Ag films as a function of films' thickness. It was found that the interplanar distance of (111) orientation decreases when the film thickness increases and tends to be close to that of bulk material. The compressive strains also decrease with increasing thickness.     

Rugate filter made with composite thin films by ion-beam sputtering

Composite films of Ta-Si oxide with refractive indices that varied from 1.48 to 2.15 were realized by using rf ion-beam sputtering. All the composite films were amorphous and had a surface roughness of less than 0.3 nm. The inhomogeneity of the composite was discussed, and a rugate filter was designed and fabricated by automatic computer control.     

Boron doping of amorphous hydrogenated silicon films prepared by r.f. sputtering

Amorphous hydrogenated silicon (a-Si:H) films 1 μm thick were prepared at 190 and 250 °C by r.f. sputtering in an Ar-H₂-B₂H₆ gas mixture whose composition Y_g = [B₂H₆]/([Ar] + [H₂]) was varied between zero and 10^-2. Measurements of the optical gap E₀ and the dark conductivity σ_d give evidence for the existence of three regions as a function of Y_g. Up to Y_g = 10^-6, the conductivity activation energy E_a increases towards the intrinsic value E₀/2. For Y_g between 10^-6 and 10^-3, E₀ and E_a decrease to 1.5 eV and 0.4 eV respectively, indicating that efficient p-type doping is achieved. At higher diborane concentrations a boron-rich a-Si:B:H compound is formed which is not conductive. The photoconductivity ratio σ_ph/σ_d reaches its maximum value (of 10³) at Y_g ≈ 10^-6 and drops to unity for Y_g ? 10^-4. The loss in σ_ph is related to an increase in the density of states near the Fermi level as revealed by the onset of an important hopping conductivity on the σ_d curves.     

溅射Si/Ge多层膜及其发光誊性研究

采用离子束溅射技术,在玻璃衬底上制备了不同周期数的Si/Ge多层膜样品.利用X射线小角衍射、Raman散射光谱和室温光致发光(PL)对样品进行表征.结果表明,2.0～2.3eV之间的发光带是由薄膜中的各种缺陷形成的;1.77～1.84eV之间的发光带来自薄膜中的非晶结构和晶粒间的缺陷;1.53eV发光峰则可能源于纳米Ge晶粒发光.     

Residual stress of graded-index-like films deposited by radio frequency ion-beam sputtering

In this study, Ta₂O₅-SiO₂ composite films with various proportions of Ta₂O₅ were prepared by radio frequency ion-beam sputtering deposition. The residual stress of each composite film was analyzed. The residual stresses of different graded-index-like layers made of composite films were studied. The results show that the residual stress of a single layered composite film was lower than that of pure SiO₂ or a pure Ta₂O₅ film. Furthermore, when the composite film was made graded-index-like, the residual stress was reduced.     

TiO2--Ta2O5 composite thin films deposited by radio frequency ion-beam sputtering

TiO2--Ta2O5 composite films were prepared by a radio frequency ion-beam sputtering deposition process, and the refractive indices and extinction coefficients of the composite films were found to be between those of the TiO2 and Ta2O5 films. The structure of the as-deposited films was amorphous, and the surface roughness was approximately 0.1 nm. The residual stress of the composite films was less than that of pure TiO2 film. The structure of the composite films after annealing was amorphous, with low surface roughness and slightly increased residual stress. The film containing 6.3% TiO2 displayed better properties than either the pure TiO2 or the pure Ta2O5 film.     

Structural, optical and electrical properties of AZO/Cu/AZO tri-layer films prepared by radio frequency magnetron sputtering and ion-beam sputtering

Highly conducting tri-layer films consisting of a Cu layer sandwiched between Al-doped ZnO (AZO) layers (AZO/Cu/AZO) were prepared on glass substrates at room temperature by radio frequency (RF) magnetron sputtering of AZO and ion-beam sputtering of Cu. The tri-layer films have superior photoelectric properties compared with the bi-layer films (Cu/AZO, AZO/Cu) and single AZO films. The effect of AZO thickness on the properties of the tri-layer films was discussed. The X-ray diffraction spectra show that all films are polycrystalline consisting of a Cu layer with the cubic structure and two AZO layers with the ZnO hexagonal structure having a preferred orientation of (0 0 2) along the c-axis, and the crystallite size and the surface roughness increase simultaneously with the increase of AZO thickness. When the AZO thickness increases from 20 to 100 nm, the average transmittance increases initially and then decreases. When the fixed Cu thickness is 8 nm and the optimum AZO thickness of 40 nm was found, a resistivity of 7.92 × 10⁻⁵ Ω cm and an average transmittance of 84% in the wavelength range of visible spectrum of tri-layer films have been obtained. The merit figure (F_TC) for revaluing transparent electrodes can reach to 1.94 × 10⁻² Ω⁻¹.