The fine probe forming capabilities of an analytical electron microscope combined with the development of related spectroscopies, diffraction and imaging techniques, makes it possible to obtain structural and chemical information from multiphase materials at high spatial resolution. These microanalytical methods are described with relevant examples from our studies of compounds in the A12O3-AIN pseudobinary system, a potential window material, low-pressure synthesized diamond, diamond-like carbon and hydrocarbon films. A comprehensive example of the characterization of a novel AION poltypoid structure (32H), illustrative of both the information content obtainable from these techniques at any particular level of resolution and the need to employ all the complementary methods of analysis, is discussed. Efforts to characterize a variety of diamond-like carbon films by the measurements of both the low-loss plasmon resonances and the fine strcture in the core-loss edges observable in the energy-loss spectrum, to obtain sp3/sp2 ratios are outlined. The electronic structure of thin film diamonds, synthesized by a plasma enhanced chemical vapour deposition method, has been shown to be in agreement with band structure calculations.

Measurements of the current noise power spectrum of the photoconducting insulators CdS and CdSe irradiated with monochromatic light of different wavelength A are reported.

It is shown that there is an abrupt change of about one order of magnitude in the low frequency power density of the noise when A crosses the photoconductor gap value Ag and the photocurrent and the device conductance are kept constant by varying the light intensity.

The effect is explained in terms of an abrupt increase of the carrier recombination rate when the photon energy becomes larger than the energy gap of the photoconductor. Possible applications of these results are briefly discussed.

Cadmium telluride and gallium arsenide remain the only viable materials for electro-optic modulator applications in the 10 μm wavelength range. Primarily the modulators are used as Q switches, cavity dumpers, amplitude modulators, and frequency modulators for infrared applications, such as laser radar and guidance systems. Designers of optical and electrical systems incorporating these modulators require accurate values for the electro-optic coefficient, r41.

A test arrangement, based on a modified version of the cross polarizer technique, was used to measure the electro-optic coefficients for cadmium telluride and gallium arsenide single crystals. The first part of this paper describes our test arrangement for measuring the r41 coefficient. The second part of the paper will discuss the test results. The r41 coefficient for CdTe was found to be 5.5 × 10−12 m/V in the unclamped region and 4.1 × 10−12 m/V in the clamped reion. Values for the r41 coefficient in GaAs were found to be 1.3 × 10−12 m/V and 1.9 × 10−12 m/V in the unclamped and clamped regions, respectively. All measurements were at 10.6 μm. Also investigated are the piezoelectric resonance values for both materials and the effect the resonances have on the measured r41 coefficient in the clamped and unclamped regions.

KNbO3 is a strong candidate as a material for use as channel waveguides due to a high electrooptic figure of merit. High quality single crystals are difficult to obtain due to incongruent melting of the compound. Control of cation concentration and oxygen incorporation are problems encountered in current thin film processing routes.

In order to overcome the problems discussed above, an ion beam deposition system featuring a computer-controlled rotatable target holder and quartz crystal resonator (QCR) feedback loop has been developed. Multicomponent films are produced via sputtering from elemental or compound targets sequentially exposed to an ion beam. Initial results are presented on the use of this new technique for the deposition of KNbO3. Pressed KNbO3, Nb2O5, and KO2 powders were used as sputtering targets. By varying the programmed thickness of deposited film from each target being sputtered, the ratio of K:Nb could be reproducibly controlled. The variation in sticking coefficients due to substrate temperature was also compensated for in this manner.

Thin films were analyzed by X-ray diffraction and TEM to determine phases present and film microstructure. Film morphology and composition has been studied as a function of substrate temperature, layer thickness, and ion beam process parameters. The relation between deposition parameters and film characteristics are discussed.

In ionized cluster beam (ICB) deposition, crystal properties can be controlled by changing the acceleration voltage and the ionization current. Therefore, the physical and chemical characteristics of the deposited films can be controlled. This controllability in ICB deposition allows one to deposit new optical films. These films are expected to have many new applications over optical range from x-ray to visible. This paper describes film examples for an X-ray mirror with low stray scattering, for an excimer laser mirror with very high damage threshold power and for dielectric optical coatings. These results show that the ICB technique offers much potential for developing new optical thin films in a wide range of applications.

Thin CaF2 films were grown at low temperatures (20°C) using an ion-beamassisted laser evaporation method. Smooth, dense, environmentally stable coatings with bulk refractive indices were produced. This technique was applied to deposit mid-wave IR dichroic filters using CaF2 and Ge layers onto cold substrates.

Thin dielectric films for optical applications are deposited on substrates using a variety of techniques including reactive sputtering, solgel reaction, and ion assisted plasma deposition. This transmission electron microscopy study characterizes optical coatings produced by the above deposition techniques and shows how changes in deposition conditions change microstructure and as a result the optical properties.

Vanadium dioxide was deposited on sapphire substrates by RF reactive sputtering. Biasing of substrates during deposition was used to alter both resistivity and infrared transmission of VO2 thin films. It has been found that as the negative dc bias potential is increased, films in the metallic state show an increased transmittance of IR wavelengths between 2.5 and 6 μm. Also, the resistivity ratio of the semiconductor to metal phase as a function of bias potential is found to reach a maximum value after which further increases in bias cause degradation of electrical properties. X-ray diffraction analysis was used to study film composition.

ZnO layers were grown by organometallic chemical vapor deposition. Films were deliberately doped with nitrogen by incorporating ammonia into the ambient during growth. The resistivity of the films depended strongly on the ammonia partial pressure. The layers were n-type with resistivities in the range of 0.1 − 360 ohm-cm. The films exhibited strong ultraviolet nearbandedge photoluminescent emission. Emission was ascribed to recombination of bound excitons at neutral acceptors, presumably involving substitutional nitrogen.

Recently, much interest has been created in laser driven chemical reactions and their application towards photodeposition of thin films of metals on semiconducting substrates. The next logical step is to verify the capability of this technique in making adequate electrical contacts for microelectronic fabrications and for circuit writing. Some work in this direction has been reported for Iron and Tungsten. However, deposition of gold has not been reported so far, even though it is very significant from the technological point of view. Therefore, we are proposing here a method for photodeposition of gold.

this pupose, Pyridine gold (III) trichloride was found to be adequated and it was prepared by a conventional method, then dried under vacuum for 48 hours. A concentrated solution was made by dissolving it in Dimethyl sulfoxide. A tiny drop of it was put on the substrate and exposed to radiation 488 nm, obtained from an argon ion laser. The time of photodeposition depends upon the power of the beam; for 2 watt/mm2 and for four to six minutes of continuous exposure, good, low noise, reliable and nearly ohmic contacts were obtained.

The method is found to be suitable for both conventional and non conventional semiconductors such as ZnTe, doped and undoped ZnSe, and diluted magnetic semiconductors such as Zn1−xMnxSe for which normally used methods are not applicable. The present technique can also be extended to the hiqh Tc superconductor YBa2Cu3O7. The possible mechanism of photodeposition is also discussed.

The sol-gel processing of ferroelectric thin films is being investigated at Battelle. The ferroelectric materials included in this study are PbTiO3, Pb(Zr, Ti)O3 (PZT), and KNbO3. The sol-gel processing and crystallization of these films on fused silica, silicon, alumina, and single crystal SrTiO3 substrates is described.

Sol-gel derived PbTiO3 thin films crystallized into the expected tetragonal perovskite structure when heated to 500 C and above. However, the crystallization of sol-gel PZT (20/80) thin films was found to be substratedependent. The heat-treated PZT films were amorphous when deposited on silica and silicon substrates. Crystalline perovskite PZT films were produced on alumina substrates, and epitaxial PZT films were produced on single-crystal SrTiO3. Heat treatment of sol-gel KNbO3 films on silicon and alumina substrates resulted in the crystallization of a variety of non-perovskite phases, but epitaxial growth of KNbO3 was observed on single crystal SrTiO3.

Photoinduced periodic structures in silica glass fibers doped with germanium and phosphorous will be discussed.

Doping with hydrogen is shown to reduce the sensitivity of optical fibers to form optical attenuation bands as a result of ionizing radiation and to increase the recovery rate in the near infrared after the exposure. In this case silicon hydride is shown to form in low-OH, pure silica fibers upon Co-60 irradiation. The ratio of radiolytically induced changes in silicon hydride to silicon hydroxide is estimated to be greater than ten. The more numerous radiolytic formation of SiH species implies the participation of oxygen vacancy type defects in the radiolytic process.

The influence of ion beam induced lattice damage on the refractive indices is evaluated for He+ implanted planar waveguides in lithium niobate (LiNbO3) and potassium niobate (KNbO3 ). KNbO3 exhibits a higher sensitivity for ion beam induced refractive index alterations. In order to suppress leaky modes, varying angle implantation has been applied. The annealing of electronic damage in both crystals is compared. While it requires heating up to 200°C for LiNbO3, the electronic damage in KNbO3 has been found to anneal at much lower temperatures. Annealing takes place even at room temparature, the electronic damage vanishes almost completely within 100 days.

Si implantation followed by furnace annealing has been used to produce the mixing of GaAs/AlGaAs multiquantum well (MQW) structures grown by MOVPE. Masked implants have been used to fabricate stripe optical waveguides. Results are presented here for the effect of the ion dose and the annealing time and it is shown that complete mixing occurs for a 1015 cm−2 dose of 500 keV Si+ after annealing at 750 °C for two hours. Waveguides fabricated using this process showed a minimum TE mode propagation loss of 33 dB cm−1 at a wavelength of 1.15 μm.

Optical channel waveguiding has been observed in a structure consisting of a silicon nitride ridge on a multilayer GaAlAs heterostructure. The silicon nitride layer was deposited and then patterned to form 3.5 micron wide ridges. The optical field intensity radiating from the endface of the channel waveguide is found to have two peaks symmetric about the center of the silicon nitride ridge. Raman microprobe spectroscopy indicates a significant stress-induced shift in the GaAs longitudinal phonon frequency. Rapid thermal annealing reduces the stress and changes the optical field intensity distribution to a single symmetric peak.

The microstructural development of Ti:LiNbO3 optical waveguides as a function of annealing time and temperature was studied using transmission electron microscopy. The morphological evolution of the deposited Ti film can be characterized by three stages: (i) oxidation beginning at low temperatures, (ii) coarsening and secondary grain growth of the oxide film at higher temperatures and (iii) eventual film breakup and void formation. Secondary grain growth is driven by minimization of interfacial energy of grains which have a special epitaxial relationship with respect to the LiNbO3 substrate.

Rapid thermal annealing has been used to initiate diffusion of Ti in LiNbO3 for the fabrication of optical waveguides. The sample with the most rapid initial ramp of temperature to 875 C was found to have the lowest propagation loss of 1 dB/cm. In order to more fully understand these channel waveguides, we have utilized Raman microprobe spectroscopy. Preliminary results suggest that the presence of the Ti in the LiNbO3 lattice dramatically alters the Raman response.

We have demonstrated that single point diamond turning can be used to generated high optical quality finished surfaces on a new organic nonlinear crystal, L-arginine phosphate (LAP). The proper choice of cutting conditions can produce surfaces with less than 5 angstroms rms surface roughness. Local softening or melting near the cutting tool tip may play a key role in the machining process by ensuring that material is removed by ductile cutting rather than brittle fracture. At the same time, the low melting temperature of LAP makes lubrication and cooling especially important to prevent extensive melting and tool fouling. In spite of the presence of a weak cleavage plane in LAP, the surface quality is relatively insensitive to crystallographic orientation. Tool wear is apparently negligible, so that surface flatness is governed by the stability of the diamond turning machine. Data on residual subsurface strain and preliminary measurements of the optical damage thresholds of diamond turned LAP surfaces will be presented.

To a greater or lesser extent, all alkaline-earth oxide crystals contain hydrogen. Thermochemical reduction (TCR) of MgO and CaO crystals at high temperatures (˜2000K) and high pressures (4 to 7 atmospheres) of the metallic cation vapor (Mg and Ca respectively) results in a stoichiometric deficiency of oxygen ions, creating F centers (oxygen vacancies each with two electrons) and H− ions (protons in the anion sublattice, each occupied by two electrons). The positively-charged H− ions serve as traps for electrons excited from the F centers. Steady-state photo-excitation of the F absorption band results in F luminescence which typically extends to several minutes. This photoluminescence is detrimental for certain applications, such as tunable lasers. We have been able to reduce the hydrogen concentration prior to TCR of MgO and during TCR of CaO. The result is that the oxygen vacancies are predominantly in the one-electron F+ charge state. In contrast to the F luminescence, the decay of the F+ luminescence does not exhibit long phosphorescence. The prevalence of the F+ over the F state is found to be a function not only of the hydrogen concentration but also the severity of the thermochemical reduction.