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Interfacial phenomena, such as adhesion, friction and wear, can dominate the performance and reliability of microelectromechanical (MEMS) devices. Here, thin films made by atomic layer deposition (ALD) were tested for their tribological properties. Tribological tests were carried out with silicon counterpart sliding against ALD thin films in order to simulate the contacts occurring in the MEMS devices. The counterpart was sliding in a linear reciprocating motion against the ALD films with the total sliding distances of 5 and 20 m. Al2O3 and TiO2 coatings with different deposition temperatures were investigated in addition to Al23-TiO2-nanolaminate, TiN, NbN, TiAlCN, a-C:H [diamondlike carbon (DLC)] coatings and uncoated Si. The formation of the tribolayer in the contact area was the dominating phenomenon for friction and wear performance. Hardness, elastic modulus and crystallinity of the materials were also investigated. The nitride coatings had the most favorable friction and wear performance of the ALD coatings, yet lower friction coefficient was measured with DLC a-C:H coating. These results help us to take steps toward improved coating solutions in, e.g., MEMS applications. [ABSTRACT FROM AUTHOR]

Metal matrix nanocomposite thin films consisting of TiF3 nanoparticles embedded in TiN matrix were synthesized with the atomic layer deposition (ALD) method. TiF4, Si2H6 (or Si3H8), and NH3-based process at 350-370 °C led to nanocomposite TiF3:TiN thin films with the embedded TiF3 nanoparticles in the size range of 2-50 nm. The films grown on quartz wafers were conductive and transparent in the visible spectral range. The resistivities of the films could be controlled by the (TiF4 + Si2H6)/NH3 pulsing ratio. Transparency of the films correlated with the resistivity of the films, namely the more transparent the films were, the higher the resistivities. About 4 cm2 area photovoltaic cells with TiF3:TiN/SiO2 (1.5-20 nm)/p-Si (1-85 Ωcm)/SiO2 (1.5-20 nm)/TiN structures resulted in 0.10-0.45 V open circuit voltage and 1-2.5 μA current flow into a 120 Ω load resistor under halogen lamp (Osram 50 W, 240 V bulb, 2800 K) illumination. The mechanism of the photovoltaic effect in these structures is not known in detail, but it is suggested that the TiF3:TiN nanocomposite functions as a partly transparent conducting electrode on the silicon wafer forming a MIS-type silicon photovoltaic cell. This new material and its derivatives may have multiple applications in current and future photonic devices. TEM images of the TiF3:TiN nanocomposite thin film. The plan view image is a dark field image showing the TiF3 crystallites as bright spots, whereas the cross sectional image is a bright field image showing the TiF3 crystallites as dark spots. [ABSTRACT FROM AUTHOR]

The scratch test method is widely used for adhesion evaluation of thin films and coatings. Usual critical load criteria designed for scratch testing of coatings were not applicable to thin atomic layer deposition (ALD) films on silicon wafers. Thus, the bases for critical load evaluation were established and the critical loads suitable for ALD coating adhesion evaluation on silicon wafers were determined in this paper as LCSi1, LCSi2, LCALD1, and LCALD2, representing the failure points of the silicon substrate and the coating delamination points of the ALD coating. The adhesion performance of the ALD Al2O3, TiO2, TiN, and TaCN+Ru coatings with a thickness range between 20 and 600 nm and deposition temperature between 30 and 410 °C on silicon wafers was investigated. In addition, the impact of the annealing process after deposition on adhesion was evaluated for selected cases. The tests carried out using scratch and Scotch tape test showed that the coating deposition and annealing temperature, thickness of the coating, and surface pretreatments of the Si wafer had an impact on the adhesion performance of the ALD coatings on the silicon wafer. There was also an improved load carrying capacity due to Al2O3, the magnitude of which depended on the coating thickness and the deposition temperature. The tape tests were carried out for selected coatings as a comparison. The results show that the scratch test is a useful and applicable tool for adhesion evaluation of ALD coatings, even when carried out for thin (20 nm thick) coatings. [ABSTRACT FROM AUTHOR]