Optical bistability in amorphous Si–C alloys and amorphous alloy interference filters

The heat flow in evaporated thin film interference filters with CdS spacer and an optional CdSe absorption layer is investigated, analyzing the dynamics of optical bistability. The influence of the spot radius r of the exciting laser beam on the switching parameters is studied experimentally and theoretically. The response to pulsed excitation of the bistable devices can be described with a relaxation time τ~r and an effective nonlinearity χ~r−2 which is inversely proportional to the heat capacity of the bistable element.

Download Full-text

Growth of near noble metal Pd and Pt thin film silicides morphology and structure

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100112464 ◽

1984 ◽

Vol 42 ◽

pp. 498-499

Author(s):

E. I. Alessandrini ◽

M. O. Aboelfotoh

Keyword(s):

Noble Metals ◽

Annealing Temperature ◽

Chemical Compounds ◽

Barrier Properties ◽

Solid State Reactions ◽

Transmission Electron ◽

Stable Chemical ◽

Metal Thickness ◽

Amorphous Si ◽

Si Films

Considerable interest has been generated in solid state reactions between thin films of near noble metals and silicon. These metals deposited on Si form numerous stable chemical compounds at low temperatures and have found applications as Schottky barrier contacts to silicon in VLSI devices. Since the very first phase that nucleates in contact with Si determines the barrier properties, the purpose of our study was to investigate the silicide formation of the near noble metals, Pd and Pt, at very thin thickness of the metal films on amorphous silicon.Films of Pd and Pt in the thickness range of 0.5nm to 20nm were made by room temperature evaporation on 40nm thick amorphous Si films, which were first deposited on 30nm thick amorphous Si3N4 membranes in a window configuration. The deposition rate was 0.1 to 0.5nm/sec and the pressure during deposition was 3 x 10 -7 Torr. The samples were annealed at temperatures in the range from 200° to 650°C in a furnace with helium purified by hot (950°C) Ti particles. Transmission electron microscopy and diffraction techniques were used to evaluate changes in structure and morphology of the phases formed as a function of metal thickness and annealing temperature.

Download Full-text

High-angle electron scattering from amorphous silicon

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100137185 ◽

1995 ◽

Vol 53 ◽

pp. 162-163

Author(s):

M. Libera ◽

J.A. Ott ◽

K. Siangchaew ◽

L. Tsung

Keyword(s):

Electron Scattering ◽

Amorphous Material ◽

Structural Defects ◽

Constant Thickness ◽

High Angle ◽

Fast Electrons ◽

Angle Scattering ◽

Stem Image ◽

Amorphous Si ◽

Thermal Vibrations

Channeling occurs when fast electrons follow atomic strings in a crystal where there is a minimum in the potential energy (1). Channeling has a strong effect on high-angle scattering. Deviations in atomic position along a channel due to structural defects or thermal vibrations increase the probability of scattering (2-5). Since there are no extended channels in an amorphous material the question arises: for a given material with constant thickness, will the high-angle scattering be higher from a crystal or a glass?Figure la shows a HAADF STEM image collected using a Philips CM20 FEG TEM/STEM with inner and outer collection angles of 35mrad and lOOmrad. The specimen (6) was a cross section of singlecrystal Si containing: amorphous Si (region A), defective Si containing many stacking faults (B), two coherent Ge layers (CI; C2), and a contamination layer (D). CBED patterns (fig. lb), PEELS spectra, and HAADF signals (fig. lc) were collected at 106K and 300K along the indicated line.

Download Full-text