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

Internal Stress and Young's Modulus of Vacuum Deposited Germanium Films

The changes in the structure and properties of MgF2 and ZnS films prepared by ion-beam-assisted deposition were investigated as a function of the power of argon ion beam irradiation. The refractive indices of MgF2 films in vacuum increased with the increase of the ion beam power, and the film density also increased slightly. It was also shown that, by the dynamic observation using Environmental Scanning Electron Microscope (ESEM), ion beam assistance increases the imperviousness to water of ZnS films. It was also observed that the wetting property for water of the film surface decreased due to ion beam assistance for both MgF2 and ZnS films.

Influence of Ion Beam Irradiation on the Structure and Properties of Dielectric Thin Films

Anatase-phase TiO2 films were prepared from amorphous TiO2 films with using a novel crystallization technology in which 13.56 MHz rf (radio frequency) plasma is applied to the film samples for few minutes without heating. The obtained anatase TiO2 films have almost the same photocatalytic degradation activity as that of the thermally-crystallized anatase TiO2 films. Although the key parameter of this plasma crystallization process is the plasma gas pressure, the best plasma gas pressure depends on the plasma gas species and applied rf power and is independent to film materials nor substrate materials. Experimental results strongly suggest that the plasma crystallization is realized by the application of alternating rf electric field into the film materials. Easiness of plasma crystallization of TiO2 films is found to depend on the film preparation conditions and this relation between crystallization easiness and preparation condition is different from the relation in the heat crystallization.

http://iopscience.iop.org/article/10.1088/1757-899X/18/17/172004/pdf

Anatase TiO2 Films Crystallized by RF Plasma Treatment

一般にPVD, CVD法として知られている薄膜形成法によって薄膜ができるときの核生成, 核成長, エピタキシーなど, 主として初期過程に関する現在までの研究成果を概観し, 現状と将来の発展の動向を示した。

Initial Stage of Thin Film Formation Process

The electrical properties have been investigated on boron-doped polycrystalline silicon films with the average grain size of 50 nm and of 370 nm. It is shown that Hall mobility is strongly dependent on the grain size, and the temperature dependence is changed by hydrogen-plasma treatment (HPT). After the treatment in the larger grain film, the mobility of about 40 cm2/V sec is obtained and it shows the boron acceptor level of 0.043 eV, which is almost the same as that of the level in monocrystalline silicon. A kink in the mobility vs temperature curve which is observed in the smaller grain film disappears by HPT. These phenomena will be discussed in relation to the density of the trapping states at the grain boundary of the films.

Akira Kinbara

Papers

Internal Stress and Young's Modulus of Vacuum Deposited Germanium Films

Influence of Ion Beam Irradiation on the Structure and Properties of Dielectric Thin Films

Anatase TiO2 Films Crystallized by RF Plasma Treatment

Initial Stage of Thin Film Formation Process

Effects of the Grain Size on the Electrical Properties of Boron-Doped Polysilicon Films