Eugeniusz Prociow

Hardness of Nanocrystalline TiO2 Thin Films

In this work results of hardness investigations of nanocrystalline TiO2 thin films are presented. Thin films were prepared by low pressure hot target reactive sputtering (LPHTRS) and high energy reactive magnetron sputtering (HERMS). In both processes a metallic Ti target was sputtered under low pressure of oxygen working gas. After deposition by LPHTRS TiO2 thin films with anatase structure were obtained and after additional post-process annealing at 1070 K, these films recrystallized into the rutile structure. Annealing also resulted in an increase of average crystallite size from 33 nm (for anatase) to 74 nm (for rutile). The HERMS process is a modification of the LPHTRS process with the addition of an increased amplitude of unipolar voltage pulses, powering the magnetron. This effectively increases the total energy of the depositing particles at the substrate and allows dense, nanocrystalline (8.7 nm crystallites in size) TiO2 thin film with the rutile structure to be formed directly. The hardness of the films was determined by nanoindentation. The results showed that the nanocrystalline TiO2-rutile thin film as-deposited using HERMS had high hardness (14.3 GPa), while the TiO2-anatase films as-deposited by LPHTRS, were 4-times lower (3.5 GPa). For LPHTRS films recrystallized by additional annealing, the change in thin film structure from anatase to rutile resulted in an increase of film hardness from 3.5 GPa to only 7.9 GPa. The HERMS process can therefore produce the TiO2 rutile structure directly, with hardness that is 2 times greater than rutile films produced by LPHTRS with additional annealing step.

Structural and surface properties of TiO2 thin films doped with neodymium deposited by reactive magnetron sputtering

Thin films were deposited using modified, high energy magnetron sputtering method from Ti-Nd mosaic targets. The amount of neodymium dopant incorporated into two sets of thin films was estimated to be 0.8 and 8.5 at.%, by means of energy dispersive spectroscopy. On the basis of x-ray diffraction method, the type of crystalline structure and crystallites size were evaluated directly after the deposition process and after additional post-process annealing at 800 °C temperature. The influence of annealing on the surface properties was evaluated with the aid of atomic force microscopy. Uniformity of the dopant distribution in titanium dioxide matrix was examined with the aid of secondary ion mass spectroscopy. Additionally, using atomic force microscope, diversification and roughness of the surface was determined. Chemical bonds energy at the surface of TiO2:Nd thin films was investigated by x-ray photoelectron spectroscopy method. Wettability measurements were performed to determine contact angles, critical surface tensions and surface free energy of prepared coatings. On the basis of performed investigations it was found, that both factors, the amount of neodymium dopant and the post-process annealing, fundamentally influenced the physicochemical properties of prepared thin films.

Influence of nanocrystalline structure and composition on hardness of thin films based on TiO2

In this work, the influence of Tb-doping on structure, and especially hardness of nanocrystalline TiO2 thin films, has been described. Thin films were formed by a high-energy reactive magnetron sputtering process in a pure oxygen atmosphere. Undoped TiO2-matrix and TiO2:Tb (2 at. % and 2.6 at. %) thin films, had rutile structure with crystallite sizes below 10 nm. The high-energy process produces nanocrystalline, homogenous films with a dense and close packed structure, that were confirmed by X-ray diffraction patterns and micrographs from a scanning electron microscope. Investigation of thin film hardness was performed with the aid of a nanoindentation technique. Results of measurements have shown that the hardness of all manufactured nanocrystalline films is above 10 GPa. In the case of undoped TiO2 matrix, the highest hardness value was obtained (14.3 GPa), while doping with terbium results in hardness decreasing down to 12.7 GPa and 10.8 GPa for TiO2:(2 at. % Tb) and TiO2:(2.6 at. % Tb) thin films, respectively. Incorporation of terbium into TiO2-matrix also allows modification of the elastic properties of the films.

Photocatalytic properties of nanocrystalline TiO2 thin films doped with Tb

In this work photocatalytic properties of TiO2 thin films doped with different amount of Tb have been described. Thin films were prepared by high energy reactive magnetron sputtering process. Comparable photocatalytic activity has been found for all doped TiO2 thin films, while different amounts of Tb dopant (0.4 and 2.6 at. %) results in either an anatase or rutile structure. It was found that the terbium dopant incorporated into TiO2 was also responsible for the amount of hydroxyl groups and water particles adsorbed on the thin film surfaces and thus photocatalytic activity was few times higher in comparison with results collected for undoped TiO2 thin films.

Optical and electrical properties of nanocrystalline TiO2:Pd semiconducting oxides

Electrical and optical properties of TiO2:Pd thin films deposited from Ti-Pd mosaic targets sputtered in reactive oxygen plasma have been studied. The properties were investigated for thin films with the Pd amount of 5.5 at. %, 8.4 at. % and 23 at. %. Based on resistivity measurements a drop from 103 down to almost 10−3Ωcm has been recorded when the Pd amount was varied from 5.5 at. % to 23 at. %, respectively. Moreover, it was shown that doping with different amounts of Pd results in the possibility of obtaining both types of electrical conduction: n-type for the TiO2 with 5.5 at. % and 8.4 at. % of Pd and p-type for the TiO2 with 23 at. % of Pd thin films. From optical measurements it has been found that as the Pd amount was increased the transmission through the thin films was reduced and position of the fundamental absorption edge was shifted toward a longer wavelength range of up to 600 nm. The optical band gap was calculated for direct and indirect transitions from optical absorption spectra. Structural properties were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). The XRD patterns displayed occurrence of the crystalline, TiO2-rutile for lower Pd amounts (5.5 at. %, 8.4 at. %), while the TiO2:Pd (23 at. %) thin films displayed XRD-amorphous behaviour. Images obtained from AFM displayed dense, nanocrystalline structure with homogenous distribution of crystallites. Additionally performed secondary ion mass spectroscopy investigation confirmed homogenous distribution of Pd in the whole thickness of the prepared thin films.

Thick/thin film thermocouples as power source for autonomous microsystems – preliminary results

Purpose – Possible application of mixed (thick/thin film) thermopiles to supply autonomous microsystems.Design/methodology/approach – PdAg/AG or PdAg/TSG thermocouples were deposited onto a circular alumina or LTCC substrates. Their thermoelectric power, resistance as well as output electrical power were characterized vs temperature gradient and chosen parameters of thermopile fabrication process.Findings – Semiconductors have high Seebeck coefficient, so investigated kind of thermopile has high output electrical power ET. It achieves 50 mV per single junction for temperature difference of about 200°C.Research limitations/implications – The problem is very high resistivity of germanium alloys, even after burn‐in process. Therefore output electrical power P is seriously reduced. To improve thermocouples properties, optimization process is required. For example, thin film layers quality can be improved, semiconductive arms width can be increased or shorter arms can be used.Originality/value – Application of...

Investigation of structural, optical and electrical properties of (Ti,Nb)Ox thin films deposited by high energy reactive magnetron sputtering

In this work the results of investigations of the titanium-niobium oxides thin films have been reported. The thin films were manufactured with the aid of a modified reactive magnetron sputtering process. The aim of the research was the analysis of structural, optical and electrical properties of the deposited thin films. Additionally, the influence of post-process annealing on the properties of studied coatings has been presented. The as-deposited coatings were amorphous, while annealing at 873 K caused a structural change to the mixture of TiO2 anatase-rutile phases. The prepared thin films exhibited good transparency with transmission level of ca. 50 % and low resistivity varying from 2 Ωcm to 5×10−2 Ωcm, depending on the time and temperature of annealing. What is worth to emphasize, the sign of Seebeck coefficient changed after the annealing process from the electron to hole type electrical conduction.

Structure and morphology of Ge(Au) sputtered films with useful Seebeck effect

Abstract The results of investigations concerning the structural and the thermoelectric properties of Ge(Au) sputtered films under pulsed voltage operation of magnetron are described. The film properties are discussed as a function of doping with gold (2 and 5 at%) and the substrate temperature during deposition (360–1040 K). Almost all as-deposited films were polycrystalline and contained crystallites of both Ge and Au phases. The Seebeck coefficient and the electrical conductivity were observed to increase with increasing substrate temperature during sputtering. In general, depending upon the sputtering conditions, compressive or tensile stresses of the order of − 1.8 × 10 8 Pa to 2.7 × 10 8 Pa were observed in Ge. The tensile stress in Au was observed to increase with increasing substrate temperature. The experimental results are discussed in terms of microstructure changes. The proper deposition conditions for optimizing internal stress, Seebeck coefficient and film resistivity can be obtained.

Microstructure of nanocrystalline titanium dioxide thin films deposited on silicon

In present paper results of structural investigations of thin films of titanium dioxide (TiD;) manufactured by modified magnetron sputtering process have been outlined XRD studies have shown that application of monocrystalline silicon wafers ensured fabrication of thin films with a high quality nanocrystalline structure with average size of grains in the range of (20 -i- 50) nm. It was stated that thin films fabricated by the modified method of magnetron sputtering were contracted at some preferred directions.

Temperature coefficient of resistance compensation method for thin film precise resistors

Abstract A method is presented for temperature coefficient of resistance (TCR) compensation based on the use of an intermittent pattern resistor. The condition for compensation to achieve zero TCR was found from an analysis of the equivalent circuit. This makes it possible to calculate the ratio of the number of squares in the resistive and conducting paths of the intermittent pattern for given initial layer parameters. It is possible to achieve zero TCR only if the conducting layer is connected to a resistive layer of negative TCR. The method has been applied to a circuit made of TaN, NiCr and nickel layers. The results confirm the idea of the compensation method. This method is particularly suitable for the design of thin film circuits made of conventional materials.