1. Introduction and overview 2. Film stress and substrate curvature 3. Stress in anisotropic and patterned films 4. Delamination and fracture 5. Film buckling, bulging and peeling 6. Dislocation formation in epitaxial systems 7. Dislocation interactions and strain relaxation 8. Equilibrium and stability of surfaces 9. The role of stress in mass transport.

Thin Film Materials: Stress, Defect Formation and Surface Evolution

Electrical and optical spectroscopic studies of TiO2 anatase thin filmsdeposited by sputtering show that the metastable phase anatase differs in electronic properties from the well‐known, stable phase rutile. Resistivity and Hall‐effect measurements reveal an insulator–metal transition in a donor band in anatase thin films with high donor concentrations. Such a transition is not observed in rutile thin films with similar donor concentrations. This indicates a larger effective Bohr radius of donor electrons in anatase than in rutile, which in turn suggests a smaller electron effective mass in anatase. The smaller effective mass in anatase is consistent with the high mobility, bandlike conduction observed in anatase crystals. It is also responsible for the very shallow donor energies in anatase. Luminescence of self‐trapped excitons is observed in anatase thin films, which implies a strong lattice relaxation and a small exciton bandwidth in anatase. Optical absorption and photoconductivity spectra show that anatase thin films have a wider optical absorption gap than rutile thin films.

Electrical and optical properties of TiO2 anatase thin films

In this paper we present a novel and versatile t e c h n i q u e f o r t h e p r o d u c t i o n o f u l t r a f i n e m e t a l p a r t i c l e s by evaporation from a temperature‐regulated oven containing a reduced atmosphere of an inert gas. An extensive investigation of particles of oxidized Al, with diameters of 3 to 6 nm, has been performed. We have also studied ultrafine particles of Mg,Zn, and Sn produced in the same manner. A supplementing investigation has been carried out for particles of Cr, Fe, Co, Ni, Cu, and Ga, as well as larger Al particles, produced by ’’conventional’’ inert‐gas evaporation from a resistive filament. Diameter as a function of evaporation rate, inert‐gas pressure, and the kind of inert gas are reported. Crystalline particles smaller than 20 nm look almost spherical in the electron microscope, while larger ones often display pronounced crystal habit. S i z e d i s t r i b u t i o n s have been investigated in detail, and consistently the logarithm of the particle diameter has a Gaussian distribution to a high precision for the smallest sizes, whereas larger particles deviate from such a simple behavior. A statistical growth model, based on the Central Limit Theorem, has been formulated for liquidlike coalescence of particles; this theory accounts satisfactorily for all our data, as well as for most size distributions published in the literature. Applications of the model to colloids, discontinuous films, and supported catalysts are discussed. By comparing size distributions for particles produced by a variety of techniques we found a number of empirical rules for the width of the distributions, as defined by a (geometric) standard deviation σ. For crystalline inert‐gas‐ evaporated particles we obtained consistently 1.36?σ?1.60; for coalescing islands in discontinuous films we found 1.22?σ?1.34; and similar rules are applicable to colloids, supported catalysts, and to ultrafine droplets.

Ultrafine metal particles

On the basis of different types of experiments, the authors develop implicitly the model of surface-enhanced Raman scattering (SERS) of adsorbates on metal surfaces. The long-range enhancement by resonances of the macroscopic laser and Stokes field is separated quantitatively from the metal electron-mediated resonance Raman effect. The latter mechanism proceeds by increased electron-photon coupling at an atomically rough surface and by temporary charge transfer to orbitals of the adsorbates. This model can account for the chemical specificity and vibrational selectivity of SERS and (partly) for the SERS specificity of the various metals.

https://iopscience.iop.org/article/10.1088/0953-8984/4/5/001/pdf

Surface-enhanced Raman scattering

Metasurfaces: From microwaves to visible

Isothermal desorption of indium from √31−In and √3−In on silicon (111) surfaces

The character of a planar tensile stress (observed) in evaporated gold films has been investigated by means of bending method and X-ray diffraction. It has been found that stress increases with increasing film thickness in films thinner than 1000 A and approaches to a certain values of the order of 109 dyn/cm2 in thicker films. By annealing, the bending of the substrate increases, showing the increase of the stress in films but the X-ray diffraction shows that the stress in crystal grains in films decreases.

https://iopscience.iop.org/article/10.1143/JJAP.4.243/pdf

Internal Stress of Evaporated Thin Gold Films

The breakdown of alumina rf windows being used in high‐power rf systems of accelerators has been investigated. The puncture and the thermal fracture often taking place in s‐band pulsed rf systems and in UHF cw rf systems, respectively, are found to be induced by alumina surface heating due to an electron multipactor bombardment accompanied by a luminescence of alumina. It is ascertained that TiN coatings on the alumina window suppress the multipactor, and that the window duration for breakdown is dependent on the microstruture of the alumina ceramic.

Breakdown of alumina rf windows

A method for obtaining the optical constants and thickness of thin metal films during deposition using an automatic recording ellipsometer is described. The restored azimuth ψ, the differential phase change on reflection Δ and the transmittance T have been continuously meaured during the film deposition. The optical constants and the packing factor are calculated from these three quantities and are given as functions of film thickness for various deposition conditions.

http://iopscience.iop.org/article/10.1143/JJAP.8.559/pdf

Continuous Ellipsometric Determination of the Optical Constants and Thickness of a Silver Film during Deposition

Thin films of LaB6 are prepared by a radio frequency (rf) magnetron sputtering technique. The effect of sputtering conditions on the film properties of internal stress and crystalline orientation are investigated. The film deposited at low pressures (<1 Pa) has a strong compressive stress as high as 109 Pa. As the pressure of Ar discharge gas decreases, the internal stress becomes greater and the preferred orientation is transformed in the sequence: (100)→(110)→(111). This behavior can be explained as an energetically favorable structure of LaB6 film by taking both the surface energy and the strain energy into account. An application of a negative bias (−20 V) to substrates results in a greater stress, so that the (110) and (111) orientation becomes more preferential.

Akira Kinbara

Papers

Isothermal desorption of indium from √31−In and √3−In on silicon (111) surfaces

Internal Stress of Evaporated Thin Gold Films

Breakdown of alumina rf windows

Continuous Ellipsometric Determination of the Optical Constants and Thickness of a Silver Film during Deposition

Structure modification of radio frequency sputtered LaB6 thin films by internal stress