The effect of argon pressure, residual oxygen and exposure to air on the electrical and microstructural properties of sputtered chromium thin films

Chromium thin films were deposited on SiO₂/Si wafers using two sputtering systems with different levels of cleanliness, and at argon sputtering pressures varying between 0.13 and 0.93 Pa. Films from the two systems grown under identical sputtering conditions had significantly different resistivity values that are shown to be due to differences in residual oxygen in the chambers. Electrical transport measurements were conducted on the series of grown films to investigate the influence of argon pressure on film electrical resistivity. The films morphology, microstructure and composition were characterized using scanning electron microscopy and X-ray photoelectron spectroscopy. Significant differences were found in Cr thin films sputtered at different sputtering pressures; differences in resistivity performance and microstructure were noted. This change was shown to be due to the transition from porous structure to a denser microstructure. The Cr films sputtered at high pressure contained large quantities of oxygen when exposed to air. Some of the oxygen is added to the film during the deposition depending on the deposition rate and the base pressure of the sputtering system. The rest is incorporated into the film once it is exposed to air. The amount of oxygen added at this stage depends on the structure of the film and would be minimal for the films deposited at low sputtering pressures.     

A simultaneous annealing effect during high-temperature electroless copper plating using the non-isothermal deposition method

A simultaneous annealing effect on the electroless-plated copper films deposited using the non-isothermal deposition (NITD) method was demonstrated. The Cu films were deposited onto NiMoP/Si substrates and their properties, such as microstructure, resistivity, and crystalline texture, were studied. At a deposition temperature of 400 °C, we found that the resistivity of the as-deposited Cu films was as low as 2.4 μΩ·cm, and X-ray diffraction showed a remarkable (111)/(200) peak ratio of 18.7. It reveals that the NITD system has an excellent capability to deposit and anneal a metal film in one step and does not require any post-annealing process.     

Structural and electrical properties of room temperature pulsed laser deposited and post-annealed thin SrRuO3 films

Good quality strontium ruthenate (SrRuO₃) thin continuous films (15 to 125 nm thick) have been synthesized on silicon (100) substrates by room temperature pulsed laser deposition under vacuum followed by a post-deposition annealing, a route unexplored and yet not reported for SrRuO₃ film growth. The presence of an interfacial Sr₂SiO₄ layer has been identified for films annealed at high temperature, and the properties of this interface layer as well as the properties of the SrRuO₃ film have been analyzed and characterized as a function of the annealing temperature. The room temperature resistivity of the SrRuO₃ films deposited by laser ablation at room temperature and post-annealed is 2000 μΩ·cm. A critical thickness of 120 nm has been determined above which the influence of the interface layer on the resistivity becomes negligible.     

Electrical properties of thin oxidized aluminium films

Thin aluminium films of thickness 40 to 200 nm were deposited on to glass substrates at 573 K in a high vacuum. The deposition was carried out layer by layer and the interfaces between these layers were exposed to oxygen. The electrical resistivity was studied as a function of the film thickness, annealing time, annealing temperature and oxygen pressure. The temperature coefficient of resistivity and the activation energy for the conduction electrons were studied as a function of the film thickness and oxygen pressure. Fuchs-Sondheimer theory for electrical conduction was applied to the experimental results. The mean free path of the conduction electrons was calculated as a function of temperature and agreed well with the theoretical relation.     

镍铬合金薄膜的研究进展

镍铬合金薄膜是重要的精密电阻和应变电阻薄膜材料.简述了镍铬合金薄膜的3种制备方法:真空蒸发沉积、磁控溅射沉积和离子束沉积;讨论了基底、工作气压、沉积时间等薄膜制备工艺参数以及退火工艺对薄膜性能的影响.重点叙述了镍铬合金薄膜、改良型镍铬合金膜、含氮镍铬合金膜、镍铬合金多层膜和纳米镍铬合金薄膜等膜系的特征.阐明了制备具有高电阻率、低电阻温度系数、高应变灵敏系数、良好的热稳定性等优异综合性能的镍铬合金薄膜的新工艺发展趋势.     

Electrical properties of thin metal zinc films

Thin metal zinc films 40 to 200 nm thick are deposited by thermal evaporation at room temperature onto glass substrates with a deposition rate of 0.2 to 0.7 nm sec^–1. The electrical resistivity is measured as a function of film thickness, deposition rate and annealing temperature. The experimental results show that electrical resistivity decreases as the film thickness, deposition rate and annealing temperature increase, while the temperature coefficient of resistivity increases with the increase in the film thickness. The calculated values of the activation energy for the conduction electrons increases as the film thickness and deposition rate increase. The well known Fuchs-Sondheimer model is applied for zinc films. The theoretically calculated values for the electrical resistivity and the temperature coefficient of resistivity are in good agreement with the experimental results.     

The influence of annealing temperature on the structural, electrical and optical properties of ion beam sputtered CuInSe2 thin films

CuInSe₂ (CIS) thin films were prepared by ion beam sputtering deposition of copper layer, indium layer and selenium layer on BK7 glass substrates followed by annealing at different temperatures for 1 h in the same vacuum chamber. The influence of annealing temperature (100-400 °C) on the structural, optical and electrical properties of CIS thin films was investigated. X-ray diffraction (XRD) analysis revealed that CIS thin films exhibit chalcopyrite phase and preferential (112) orientation when the annealing temperature is over 300 °C. Both XRD and Raman show that the crystalline quality of CIS thin film and the grain size increase with increasing annealing temperature. The reduction of the stoichiometry deviation during the deposition of CIS thin films is achieved and the elemental composition of Cu, In and Se in the sample annealed at 400 °C is very near to the stoichiometric ratio of 1:1:2. This sample also has an optical energy band gap of about 1.05 eV, a high absorption coefficient of 10⁵ cm⁻¹ and a resistivity of about 0.01 Ω cm.     

Optoelectronic properties of sputter-deposited Cu2O-Ag-Cu2O treated with rapid thermal annealing

Cu₂O and two types of Cu₂O-Ag-Cu₂O (CAC) multilayered thin films were deposited on glass substrates using DC-magnetron sputtering. For CAC films, the mass thickness of Ag layer was controlled at 3 nm. After deposition, some of these films were annealed using a rapid thermal annealing (RTA) system at 650 °C, in order to create embedded Ag particles. AC films were used to study the clustering effect of Ag in Ar atmosphere, as well as for forming the 2nd type of CAC film by covering another Cu₂O layer on the annealed AC structure. A UV-VIS-NIR photometer, a Hall measurement system, and a I-V measurement system were used to characterize the optical and electrical properties of these films with and without RTA. The results show that 2-dimensional Ag layer can transform into many individual particles due to its high surface tension at annealing temperature, no matter when the annealing was carried out. For CAC films, without annealing, the optical transmission and the resistivity are decreased with the inserted Ag layer. After annealing, both the transmission and resistivity are increased, possibly due to the clustering effect of Ag layer. Most importantly, it is found that the embedded Ag particles can increase the light absorption in the NIR-IR region, which can increase photo-induced current.     

In-situ X-ray investigations of quench-condensed thin gold films

Thin gold films were deposited on float glass substrates held at cryogenic temperatures down to 77 K and investigated in-situ using X-ray reflectometry and surface sensitive reflection mode X-ray absorption spectroscopy (XAFS). The combination of these in-situ X-ray methods with simultaneous electrical resistivity measurements yields information about the surface and volume microstructure of the deposited films as a function of the deposition temperature and their changes induced by a subsequent annealing treatment. The surface sensitive XAFS experiments clearly proved that the films exhibit a polycrystalline structure throughout the temperature range studied here. The data were fitted using a correlated Debye-model. The results show that for film deposition at low substrate temperatures < 130 K, a significantly decreasing Debye-temperature was found, reaching values of about 100 K in comparison to 165 K for the polycrystalline bulk material. This decrease was interpreted to be predominantly related to defective film regions with an increased static disorder.     

Effect of annealing on the characteristics of Au/Cr bilayer films grown on glass

Au layers with thickness of about 110 nm were sputter-deposited on unheated glass substrates coated with a Cr layer about 20 nm thick. The chamber was evacuated to a pressure of 2 Pa and then sputtering was carried out at Ar pressure of 4 Pa. The Au/Cr bilayer films were annealed in a vacuum of 5×10⁻⁴ Pa at 170°C, 180°C, 200°C and 250°C for from 5 to 120 min, respectively. Atomic force microscopy was used to observe the structural characteristic of the bilayer films. Auger electron spectroscopy was used to analyze the composition inside the Au layers. The sheet resistance of the films was measured using the four-point probe technique. The grain size of the bilayer film gradually increases with an increase in annealing temperature while its average surface roughness ranging from 4.5 to 6.8 nm does not show any systematic change with annealing temperature and time. No impurities such as carbon, nitrogen and oxygen are detected inside all of the Au layers. When the annealing temperature reaches 200°C and the annealing time exceeds 30 min, chromium atoms markedly diffuse into the Au layer. Furthermore, for the bilayer films annealed at 250°C, chromium atoms have markedly diffused into the Au layer even for annealing time of 5 min. Regardless of the increase in grain size of the Au layer, the diffusion of chromium atoms into the Au layer causes an increase in the resistivity of the bilayer film.     

Preparation of highly transparent conductive Al-doped ZnO thin films and annealing effects on properties

Aluminum-doped ZnO (ZAO) thin films were deposited on fused quartz substrates by radio frequency sputtering in pure argon ambient at 450 °C. Effects of in situ annealing temperature and annealing atmosphere on microstructure, electrical and optical properties of ZAO films have been investigated. Results showed that as-grown film without annealing treatments attained lowest resistivity of 1.1 × 10⁻⁴Ω cm. And all films performed high average transmittance greater than 90% in visible region. X-Ray diffraction (XRD), photoluminescence (PL), X-ray photoelectron spectroscopy (XPS) were utilized to characterize the microstructure properties of films. XRD results indicated that as-grown film had higher crystalline quality and larger grain size than annealed films. Al atoms replaced Zn efficiently to provide electrons stable in all samples. PL spectra revealed that high annealing temperature and oxygen atmosphere would generate more Zn vacancy (V_Zn) and oxide antisite defect (O_Zn), respectively and composition content results from XPS provided supports to this.     

Effects of annealing temperature and thickness on microstructure and properties of sol–gel derived multilayer Al-doped ZnO films

Transparent conductive multilayer Al-doped ZnO (AZO) films were prepared by the spin-on technique with rapid thermal annealing process at low temperature. The effects of annealing temperature and thickness on microstructure, growth behavior, electrical properties and optical properties of AZO films were investigated. It was found that AZO films exhibited stronger preferred c-axis-orientation, the electrical resistivity decreased as it would be expected with the increase of annealing temperature from 400 to 500 °C and the increase of the number of layers in the film from 1 to 6, but the electrical resistivity tended to keep at a certain lowest value of 2.7 × 10⁻⁴ Ω cm when the annealing temperature was above 500 °C and the number of layers did not exceed 6. The average optical transmittance of AZO films was over 90% when number of layers in the film did not exceed 4 and decreased as this number increases, but the annealing temperature had little effect on the average optical transmittance of AZO films.     

Effect of thermal annealing on the microstructure and morphology of erbium films

The effects of thermal annealing on the microstructure and morphology of erbium films were investigated by X-ray diffraction and scanning electron microscopy. All the erbium films were fabricated by electron-beam vapor deposition. The columnar grain sizes of as-received erbium films increased with the substrate temperatures and were enlarged by the coalescence and migration of grains during the high temperature annealing. The intrinsic stresses of erbium films, fabricated at a low substrate temperature (200 °C), were relaxed accompanied with the appearance of cracks on the films surface. The films deposited at 200 °C had (002) preferred orientation, and the film deposited at 450 °C had mixed (100) and (101) texture. The peak positions and the full width at half maximum of (100), (002), and (101) diffraction lines of erbium shift towards higher angles and sharply decrease during the annealing process, indicating that the stress inside the film was relaxed.     

ZnO thin films prepared by atomic layer deposition and rf sputtering as an active layer for thin film transistor

Recently, the application of ZnO thin films as an active channel layer of transparent thin film transistor (TFT) has become of great interest. In this study, we deposited ZnO thin films by atomic layer deposition (ALD) from diethyl Zn (DEZ) as a metal precursor and water as a reactant at growth temperatures between 100 and 250 °C. At typical growth conditions, pure ZnO thin films were obtained without any detectable carbon contamination. For comparison of key film properties including microstructure and chemical and electrical properties, ZnO films were also prepared by rf sputtering at room temperature. The microstructure analyses by X-ray diffraction have shown that both of the ALD and sputtered ZnO thin films have (002) preferred orientation. At low growth temperature T_s ≤ 125 °C, ALD ZnO films have high resistivity (> 10 Ω cm) with small mobility (< 3 cm²/V s), while the ones prepared at higher temperature have lower resistivity (< 0.02 Ω cm) with higher mobility (> 15 cm²/V s). Meanwhile, sputtered ZnO films have much higher resistivity than ALD ZnO at most of the growth conditions studied. Based upon the experimental results, the electrical properties of ZnO thin films depending on the growth conditions for application as an active channel layer of TFT were discussed focusing on the comparisons between ALD and sputtering.     

Effect of thermal annealing on transparent conductive LaNiO3 thin film prepared by an aqueous method

Dense, crack-free and uniform lanthanum nickel oxide (LNO) thin films were prepared by an aqueous method on various substrates, such as single crystal silicon, microcrystalline glass ceramic (GC) and amorphous glass. The effects of various thermal annealing temperatures on the microstructure, interface and electrical properties of the LNO films were investigated by XRD and SEM with the EDX and a four-probe method, respectively. It was found that with the increase in thermal annealing temperature, the LNO film on Si substrates displayed a structure change from pseudocubic to rhombohedral and was accompanied by the appearance of a NiO impure phase, while the LNO film on a GC substrate diffused into the substrate. In these cases, the film resistivity was increased. As a result, a LNO thin film with a resistivity of 2–3 × 10^–5 · m was achieved by thermally annealing at 750–800°C for 1 hour in air. The measurement of the surface resistance under different temperatures shows that the LNO film possesses better high temperature stability. Its transmittance spectrum was also observed.     

Electrical and optical properties of Zn-In-Sn-O transparent conducting thin films

Indium tin oxide (ITO) is one of the widely used transparent conductive oxides (TCO) for application as transparent electrode in thin film silicon solar cells or thin film transistors owing to its low resistivity and high transparency. Nevertheless, indium is a scarce and expensive element and ITO films require high deposition temperature to achieve good electrical and optical properties. On the other hand, although not competing as ITO, doped Zinc Oxide (ZnO) is a promising and cheaper alternative. Therefore, our strategy has been to deposit ITO and ZnO multicomponent thin films at room temperature by radiofrequency (RF) magnetron co-sputtering in order to achieve TCOs with reduced indium content. Thin films of the quaternary system Zn-In-Sn-O (ZITO) with improved electrical and optical properties have been achieved.The samples were deposited by applying different RF powers to ZnO target while keeping a constant RF power to ITO target. This led to ZITO films with zinc content ratio varying between 0 and 67%. The optical, electrical and morphological properties have been thoroughly studied. The film composition was analysed by X-ray Photoelectron Spectroscopy. The films with 17% zinc content ratio showed the lowest resistivity (6.6 × 10^− 4 Ω cm) and the highest transmittance (above 80% in the visible range). Though X-ray Diffraction studies showed amorphous nature for the films, using High Resolution Transmission Electron Microscopy we found that the microstructure of the films consisted of nanometric crystals embedded in a compact amorphous matrix. The effect of post deposition annealing on the films in both reducing and oxidizing atmospheres were studied. The changes were found to strongly depend on the zinc content ratio in the films.     

Electrical resistivity of Ti-Zn mixed oxide thin films deposited by atomic layer deposition

Ti-Zn mixed oxide thin films, with thickness less than 50 nm, were grown with atomic layer deposition (ALD) technique at low temperature (90 °C) varying the composition. ALD is a powerful chemical technique to deposit thin films with thickness of few atomic layers. ALD oxide material growth is achieved by dosing sequentially the metal precursor and the oxidizing agent. Thanks to ALD nature of layer by layer growth it was possible to realize mixed metal, Ti and Zn, oxide thin films with controlled composition, simply by changing the number of cycles of each metal oxide layer. Structural and electrical properties of the prepared thin films were studied as a function of their composition. Synchrotron radiation X-ray diffraction technique was used to follow thin film crystallization during sample annealing, performed in situ. It was observed that the onset temperature of crystallization raises with Ti content, and sample structure was Zn₂TiO4 phase. Electrical resistivity measurements were performed on crystalline samples, annealed at 600 °C, revealing an increase in resistivity with Ti content.     

Post-annealing properties of aluminum-doped zinc oxide films fabricated by ion beam co-sputtering

Aluminum-doped zinc oxide (AZO) films were fabricated by using the ion beam sputter deposition (IBSD) method with dual metallic targets, Al and Zn, co-sputtered by argon ion beam in an oxygen ambient. Structural and electrical properties of AZO films before and after annealing were ex situ investigated by the X-ray diffractometer and Hall measurement with the Van der Pauw method, respectively. The intense (002) diffraction peak and simultaneously the low resistivity were observed in the as-deposited film. The resistivity of the film after 400 °C post-anneal increased more than two orders of magnitude than that of the as-deposited film resulting from the decrease of the donor concentration and mobility in the AZO film. The residual stress was derived from the results of the XRD patterns. Finally, it was found that the film resistivity increased as the annealing temperature increased and a corresponding shift of the energy band gap was observed.     

Effect of annealing on the structural and optical properties of InSe bilayer thin films

InSe bilayer thin films with different thickness were prepared on to a glass substrate by sequential thermal evaporation. Preparation and post deposition treatment conditions were optimized in order to achieve effective bilayer mixing. The influence of bilayer film thickness and annealing temperature on the structural and optical properties was investigated. The prepared films were characterized by X-ray diffraction analysis, scanning electron microscopy, energy dispersive X-ray analysis, UV-Visible spectroscopy, photoconduction and resistivity measurement. Structural studies show that the material undergoes phase transition with thickness, due to co-existence of many phases. Morphological analysis revealed that Se content plays an important role in determining the surface morphology of the film. It has been observed that grain growth and grain splitting phenomena depend on film thickness and annealing temperature. From the photoconduction measurements, the photocurrent increases rapidly when the sample is illuminated using 135 K Lux of white light. Absorption coefficient is in the order of 10⁴ cm⁻¹, makes the InSe thin film useful for the preparation of absorber layer in hybrid solar cell.     

Effect of high temperature annealing on the electrical performance of titanium/platinum thin films

In this study, the influence of post deposition annealing steps (PDA) on the electrical resistivity of evaporated titanium/platinum thin films on thermally oxidised silicon is investigated. Varying parameters are the impact of thermal loading with maximum temperatures up to T_PDA = 700 °C and the platinum top layer thickness ranging from 24 nm to 105 nm. The titanium based adhesive film thickness is fixed to 10 nm. Up to post deposition annealing temperatures of T_PDA = 450 °C, the film resistivity is linearly correlated with the reciprocal value of the platinum film thickness according to the size effect. Modifications in the intrinsic film stress strongly influence the electrical material parameter in this temperature regime. At T_PDA > 600 °C, diffusion of titanium into the platinum top layer and its plastic deformation dominate the electrical behaviour, both causing an increase in film resistivity above average.