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We have investigated the field-effect mobility of three kinds of low molecular weight spirolinked compounds, namely 2,2',7,7'-tetrakis (diphenylamino)-9,9'-spirobifluorene (spiro-TAD), 2,2',7,7'-tetrakis(biphenyl-4-yl)-9,9'-spirobifluorene (spiro-6φ) and 2,7-bis-(N,N-diphenylamino)- 2',7'-bis-(biphenyl-4-yl)-9,9'-spirobifluorene (spiro-X2). The field-effect mobilities of these materials in the saturation region are 8 x 10-4 cm2V-1s-1, 5 x 10-5 cm2V-1s-1 and 4 x 10-4 cm2V-1s-1 respectively. The atomic force microscopy images show that films prepared from these materials are amorphous with a very smooth surface and the limited field-effect mobility is due to the intrinsic behaviour of amorphous materials.

It is shown that the solid state equilibrium configuration of ZnO grain boundaries saturated with Bi-doping is a nanometer-thick amorphous film. Polycrystalline ZnO samples doped with Bi2O3 were studied using high resolution transmission electron microscopy (HRTEM) and dedicated scanning transmission electron microscopy (STEM). Samples were equilibrated below the eutectic temperature (Teutectic = 740°C) and at 1 atmosphere pressure, starting from three different initial states: one was cooled from above the eutectic temperature; a second was processed entirely below the eutectic temperature; and the third was de-segregated by applying high pressure (1 GPa) followed by annealing at 1 atmospheric pressure. In all instances, ZnO grain boundaries contain an amorphous film 1.0–1.3 ran in thickness, corresponding to a Bi excess equivalent to approximately one monolayer.

Amorphous Tb40Fe60-Fe80B20-Tb40Fe60 sandwich films were prepared by multitarget rf magnetron co-sputtering. Their magnetization and magnetostriction were studied to examine whether magnetic softening of the amorphous TbFe films could be achieved without loosing their giant magnetostriction by introducing the simple sandwich structure. The results revealed that a considerably soft in-plane magnetization (coercive force H≈ 6Oe and the squareness ratio Mr/Ms≈ 0.8) and a huge magnetostriction (λ >500ppm) could be obtained in the sandwich films at room temperature, provided that the thickness of the FeB interlayer was within the range of 10% to 40% of the total film thickness (1 μm).

The method of pulsed excimer laser ablation using KrF radiation was applied for the deposition of thin metallic elementary multilayers. Above an ablation threshold of about 5 J/cm2 an ‘explosive’ evaporation of the metallic targets occurs leading to high deposition rates of up to 5 nm/s. For different metals, the ablation threshold slightly varies leading at the same laser fluence to different growth rates as shown for Ag, Fe, Zr and Nb. By using two elementary targets and adjusting the dwelling times on both targets, Fe/Ag, Fe/Zr and Fe/Nb multilayers of different bilayer thicknesses were deposited. While Fe/Ag superstructures show crystalline phases down to a periodicity of 1 nm, Fe/Zr and Fe/Nb films are amorphous at such wavelengths. On the other side, Fe/Nb multilayers can also be amorphized by a solid state interdiffusion reaction of the elementary multilayers. The surfaces of the grown films are smooth except for a small number of droplets on the film surface.

We combine the techniques of EXAFS and XANES using synchrotron x-rays, and the corresponding techniques using electron energy loss spectroscopy (EXELFS and ELNES) to characterize and study the local atomic arrangement in thin amorphous films. These probes are complementary in that x-rays are best suited for absorption edges above 3 keV and electron energy loss spectroscopy for low energy edges, and thus this combination is very useful for amorphous materials containing both low and high Z elements. We use in addition transmission electron microscopy, electron diffraction, and electron energy loss spectroscopy in the low energy loss region. Results from amorphous T1O2 and amorphous SnO2 made by reactive sputtering are presented.

The TbFeCo thin films with dense, uniform and columnless microstructure have been prepared as magneto-optical(MO) recording media by using facing targets type of sputtering(FTS) apparatus. The Kerr rotation angle θk and the reflectivity R of TbFeCo(MO) layers with and without Al reflective layer were measured for the light wavelength λ in the range of 450–850 nm and the MO layer thickness tMO in the range of 30–150 nm. θk of the double layers type of TbFeCo/Al fms took maximum of 0.54 deg.(λ =830 nm) at tMO of about 40 nm. Furthermore, θk and R of the double layers type of films for various tMO were theoretically calculated, based on the already known optical constants of TbFe, Al and /or TbOx. Though they were qualitatively in agreement with the experimental data, there was a large discrepancy between the estimated values and the experimental results. This may be attributed to the uncertainty of available optical constants such as refractive indicies and dielectric tensors quoted in this calculation.

We have characterized the in-film stress and the mechanical constants of a growth-dominated phase-change SbTe-alloy, a material beneficially used in the line-cell phase change memory architecture. The influence of the thickness of the films (5-120 nm) and of the substrate used for its deposition (Si, SiO2 and SiC) was studied. The characterizations were carried out on both amorphous and crystalline films. The crystallization temperature was determined by the resistance changes as a function of the temperature. The mechanical characteristics of the films were measured by the wafer curvature method. We observed that the mechanical behavior of these films was strongly dependent on their thicknesses and on the substrate material. For the thinnest amorphous films, the in-film stress was highly compressive (with the largest compressive stress for films on SiC), while it tended to be very low (fully relaxed films) for films thicker than 20 nm. The amorphous films furthermore did not reveal any stress relaxation in time-dependent stress measurements. Therefore, it was not possible to quantify the viscosity of the SbTe-alloy. This result maybe related to a lower defect state in the very thin films used, or to a blocking of the defects by enhanced reactivity of these thin SbTe-alloy films with their surroundings, both resulting in the absence of relaxation in the amorphous state. Finally, the coefficients of thermal expansion (CTE) of the amorphous and crystalline SbTe-alloys were similar, 1–3×10−6 K−1. These values were comparable to the CTE's of the substrates, clearly indicating that for thin films the substrates dominate their thermal expansion behavior.

A low-temperature metal organic chemical vapor deposition (MOCVD) process for the growth of aluminum oxide for gate dielectric applications has been developed. Amorphous films were deposited on 200-mm Si(100) wafers, employing an Al β-diketonate precursor [Al(III) 2,4-pentanedionate] and H2O. Chemical and microstructural properties of films grown in a temperature range of 250-450°C were studied using x-ray photo-electron spectroscopy (XPS), xray diffraction (XRD), Rutherford back-scattering spectrometry (RBS), nuclear reaction analysis (NRA), cross-sectional (X) scanning and transmission electron microscopy (XSEM and XTEM). A design of experiment (DOE) method was used for process mapping and optimization. An optimized process window was defined for the growth of dense, amorphous films with carbon and hydrogen inclusion as low as 1 at. % and 3 at. % respectively. Post-deposition annealing studies indicated that chemical and structural film properties are generally stable up to 650°C. The electrical performance of the films was evaluated by capacitance-voltage (C-V) and currentvoltage (I-V) measurements on metal-oxide-semiconductor (MOS) structures. The dielectric constant (k) obtained was 6.7-9.6 (depending on annealing conditions), with equivalent oxide thickness (EOT) as low as 1.3 nm. Leakage current densities lower than that of equivalent SiO2 films were also achieved.

Using a new EELS analysis method the local chemical and structural changes induced by Fe segregation to two types of grain boundaries in SrTiO3 were studied. At Σ5 boundary in bicrystals Fe segregation lowers O/Ti ratio but increases substantially Ti and O concentrations in boundary region. Sr-O bond has been severely changed by the segregation as revealed by ELNES. Grain boundaries in a polycrystalline sample were covered with titania-based amorphous films where Fe content is higher but Ti and O concentrations are both lower than the bulk levels, which are strikingly different from the bicrtysal. More dopants segregated to glass pockets at triple junctions. SiO2 was detected in one of the large pocket but not at the grain boundary films within the detection limit. These observations suggest the equilibrium defect chemistry and the related space charge theory may not be the only explanation for the grain boundary segregation in SrTiO3 Local structure modification at gram boundaries can trigger dramatical change of the chemistry to a degree higher than the segregation level. The existence of titania-based amorphous films at general grain boundaries makes it better to understand Fe segregation from the two phase (SrTiO3-TiO2) equilibrium.

The origin of residual stresses were studied in both crystalline metallic films and amorphous oxide films made by ion beam assisted deposition (IBAD). Monolithic films of AI2O3 were deposited during bombardment by Ne, Ar or Kr over a narrow range of energies, E, and a wide range of ion-to-atom arrival rate ratios, R and were characterized in terms of composition, thickness, density, crystallinity, microstructure and residual stress. The stress was a strong function of ion beam parameters and gas content and compares to the behavior of other amorphous compounds such as MoSix and WS12.2 With increasing normalized energy (eV/atom), residual stress in crystalline metallic films (Mo, W) increases in the tensile direction before reversing and becoming compressive at high normalized energy. The origin of the stress is most likely due to densification or interstitial generation. Residual stress in amorphous films (Al2O3, MoSix and WSi2.2) is initially tensile and monotonically decreases into the compressive region with increasing normalized energy. The amorphous films also incorporate substantially more gas than crystalline films and in the case of Al2O3 are characterized by a high density of voids. Stress due to gas pressure in existing voids explains neither the functional dependence on gas content nor the magnitude of the observed stress. A more likely explanation for the behavior of stress is gas incorporation into the matrix, where the amount of incorporated gas is controlled by trapping.

Thin amorphous films (t=200Å) of Fe80B20 were annealed at temperatures ranging from 473K–823K and studied using extended X-ray absorption fine structure to investigate the evolution of local structure around the Fe atoms during crystallization. Modeling of the local environment around Fe using empirical standards was employed to determine the relative fraction of the crystalline phases present in annealed samples. Results illustrate the sensitivity of EXAFS in detecting the onset of crystallization in thin amorphous films and its ability to quantitatively measure the relative fraction of crystalline phases present in partially crystallized thin film samples.

We studied on a nanometer scale the tribological properties of thin silicon carbide films on Si(100) wafers and stainless steel. The coatings were fabricated from a sintered SiC target by pulsed ArF laser deposition at substrate temperatures between 20 °C and 1000 °C. Amorphous films resulted at low deposition temperatures while nanocrystalline structures developed at high deposition temperatures. An atomic force/lateral force microscope was employed to characterize the film topography and the friction behavior. The microhardness was determined from measurements utilizing a depth-sensing nanoindentation instrument. The SiC films on Si(100) exhibit a smooth surface with an average roughness Ra of a few nanometer, the amorphous films being even an order of magnitude smoother. No appreciable differences were found in microhardness and friction coefficient between amorphous and nanocrystalline films. On stainless steel, amorphous SiC coatings were obtained for deposition temperatures up to 500 °C. Their surface relief portrayed the grain boundaries of the underlying steel substrate, reflecting the ballistic nature of the deposition process. No stoichiometric films were obtained above 500 °C as the silicon from the growing film quickly dissolved in the steel substrate.

A technique has been developed for characterizing the disorder present in thin films through the measurement of their low temperature internal friction. The technique utilizes a substrate, in the form of a double paddle oscillator etched from a high purity silicon wafer, onto which the thin film of interest can be deposited. The oscillator possesses an internal friction of 3 × 10−8 at 4 K which is reproducible to within 1% upon thermally cycling to room temperature. This extremely small substrate internal friction coupled with the excellent reproducibility permits measurements of the internal friction of very thin amorphous films, with a 2 tun silica film producing a change in the internal friction of 4 × 10−9. By performing low temperature internal friction measurements on thin silica films with thicknesses ranging from 2 nm to 1000 nm, we have investigated the role of interacting defects in determining the universal nature of the anomalous low temperature thermal and elastic properties of amorphous solids. We have found no evidence for strong interactions between these tunneling defects. Other applications of the oscillator include monitoring of the crystallization of amorphous films through changes in the low temperature internal friction, internal friction measurements and vapor pressure measurements of quenched condensed rare gas solids and amorphous water ice, and internal friction studies of amorphous solids which can only be produced in thin film form.

We have characterized the surface topography of silicon films from different deposition and doping process sequences using AFM and optical reflectivity. The resulting surface structures after deposition, doping, oxide growth, and oxide removal correlate with the electrical leakage currents and breakdown voltages of double polysilicon capacitors. As-deposited amorphous films had smoother surfaces than those deposited in the crystalline state. Gas-phase diffusion doping increases the surface roughness. Only the amorphous in situ doped films retained a smooth surface following oxidation, yielding low leakage capacitors with breakdown fields above 8 MV/cm. Surprisingly, implanted amorphous films exhibited the roughest interfaces, resulting in lower breakdown fields. This study has shown that AFM provides an effective, quick, non-destructive diagnostic technique for semiconductor processing.

Silicon thin films were deposited by Electron Cyclotron Resonance PECVD using silane as a source gas at room temperature. Deposited films were crystallized either by conventional furnace annealing(FA) or by rapid thermal annealing (RTA) process. The films deposited on SiO2/Si wafer substrates were Amorphous or microcrystalline depending on the microwave power. Deposited films were annealed at 600TC in a furnace. As expected, higher crystallinity was obtained in the case of the Amorphous films than the microcrystalline films after 7.5 hours annealing. It took 15 hours at 600δC for the Amorphous films to reach their maximum crystallinity in case of FA, but it only took 1 second at 900 δC for RTA. In addition, it was shown that RTA can be applied to the rapid crystallization of Amorphous silicon thin films deposited on a fused quartz substrate utilizing a new film structure.

We have demonstrated that pulsed laser deposition (PLD) conditions, i.e. O2 partial pressure (pO2) and temperature (T), enable control over the polarity of resistance switching in PCMO (Pr0.7C0.3MnO3) i.e. unipolar resistive switching (URS) vs. bipolar resistive switching (BRS). We observe by detailed physical characterization that BRS occurs in poly-crystalline thin films while URS is seen in amorphous films – indicating the materials origin of URS vis-a-vis BRS. BRS shows attractive lower voltage operation, no forming and lower variability than URS.

Mg@ZnO thin films were prepared by DC/RF magnetron co-sputtering in (N2+O2) ambient conditions using metallic Mg and Zn targets. We present a comprehensive study of the effects of film thickness, variation of O2 content in the working gas and annealing temperature on the structural, optical and magnetic properties. The band gap energy of the films is found to increase from 4.1 to 4.24 eV with the increase of O2 partial pressures from 5 to 20 % in the working gas. The films are found to be ferromagnetic at room temperature and the saturation magnetization increases initially with the film’s thickness reaching a maximum value of 14.6 emu/cm3 and then decreases to finally become diamagnetic beyond 95 nm thickness. Intrinsic strain seems to play an important role in the observed structural and magnetic properties of the Mg@ZnO films. On annealing, the as-obtained ‘mostly amorphous’ films in the temperature range 600 to 800°C become more crystalline and consequently the saturation magnetization values reduce.

Fe-Si, Co-Ta and Co-Zr amorphous films have been deposited by using various sputtering methods (conventional rf diode sputtering, rf triode sputtering, dc Targets Facing type sputtering (dc TF sputtering) and dual ion beam sputtering (DIB sputtering)). The lower limit of the Si and Ta content to form amorphous Fe-Si and Co-Ta films changes significantly with the sputtering method. These differences between the sputtering methods are mainly caused by the differences in the plasma potential which affects the amount of ion bombardment to the film surface during sputtering,and the minimum content of Si or Ta to obtain amorphous films decreases as the plasma potential increases. These results indicate that the ion bombardment suppresses the growth of crystallites and promotes the formation of the films with amorphous structures. This is confirmed by the deposition of Co-Ta and Co-Zr amorphous films under the condition of various amount of ion bombardment by using a DIB sputtering system.

We have investigated the formation of titanium silicide films sputter deposited from a high purity (99.995%) composite TiSi2.2 target. The films, sputtered at a rate of 3.7 nm/sec, were deposited on Si(100), Si02 , and N+ Poly-Si substrates at temperatures ranging from room temperature to 425°C. Room temperature depositions produced amorphous films, while heated substrate depositions formed crystalline films with a metastable C49 TiSi2 structure. Rapid thermal processing of these films at temperatures higher than 700°C resulted in the formation of a stable C54 TiSi2 structure. Stoichiometry of the deposited films over a 10 cm diameter wafer was found to be independent of the substrate temperature. Stress in the films was measured as a function of deposition and annealing parameters. The amorphous films showed a tensile stress of about 0.1 GPa, while films deposited on substrates at 425°C had an order of magnitude higher tensile stress level.The resistivity measured on the 400°C deposited films was about half of that obtained with the films deposited at roomtemperature. A comparison between films deposited on a hot substrate and those which were rapid thermal processed is presented.

Ribbons of Fe75B25, prepared by quenching from the melt, were mostly amorpbous. After annealing at 773 K, the ribbons were entirely crystalline, with the phases Fe3B, Fe2B and α - Fe. Annealed ribbons were bombarded at RT with 4 MeV argon ions, at a damage rate of 7 × 10−4 dpa sec−1 near the surface. The Fe3B was completely converted to an amorphous form at 0.15 dpa, the lowest damage level at which amorphization of a metal alloy has been reported. The Fe2B disappeared by about 1.5 dpa. The α -Fe disappeared between 17 and 50 dpa, apparently by ion beam mixing rather than direct amorphization. Amorphous films also were prepared by sputtering at low power level, and crystallized at 773 K, which also caused sintering. Bombardment with argon ions produced major changes in resistivity and magnetic coercive force at the same low damage levels that caused amorphization of Fe3B Hc of the bombarded film was the same as in an as-quencheo amorpous ribbon. The relatively high resistivity of as sputtered amorphous film was apparently due to the porosity in the columnar cell walls. With present technology, it should be possible to produce amorphous films or structures of Fe3B at rates approaching 50 m2 hr−1.

Submicron powders, amorphous films and melt spun ribbons of various Al-Ge alloys have been analyzed to determine the relative roles of undercooling and cooling rate in the production of non-equilibrium structures. All analyses were performed in transmission electron microscopes equipped with energy dispersive x-ray spectrometers. The submicron powders, produced by electro-hydrodynamic atomization, were analyzed in their as-received condition and then annealed and/or melted using the electron beam as a local heating source. Once molten, the liquid droplets were undercooled at different cooling rates by varying the rate of beam obstruction. In this manner, a number of different microstructures were produced. These included metastable crystalline phases and mixed amorphous/crystalline structures. By combining this technique with a microscope heating stage, it was possible to carry out controlled dynamic undercooling experiments and determine phase selection as a function of undercooling and composition. The amorphous films were rapidly heated with the electron beam in the microscope and metastable as well as stable phases were produced. The results of these complementary analyses will be compared and discussed with reference to current models and theories of rapid solidification.

We report our main results on the development of un-cooled microbolometers based on hydrogenated amorphous Germanium-Silicon (a-GexSiy:H) thermo-sensing films deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD). Our research has been conducted to improve both, the structure of the devices (pixels) and the performance characteristics of the amorphous Germanium-Silicon thermosensing films.Our motivation is to produce microbolometers with much better performance characteristics (larger thermal coefficient of resistance, larger conductivity and better stability) than those available in commercial microbolometer arrays, based on boron doped hydrogenated amorphous silicon (a-Si:H,B).As part of our latest research, we also report the study of what we believe is the next generation of thermosensing films based on Silicon and Geranium amorphous films with embedded nanocrystals in the amorphous matrix (polymorphous films). Those materials have several advantages over amorphous, as a lower defect density, better stability and better transport properties.

A pulsed laser deposition system was employed to fabricate thin films of Li7La3Zr2O12 solid electrolyte. The deposition process was carried out at room-temperature, resulting in amorphous films. These as-deposited films had a large optical band gap of 5.13 eV, and exhibited a lithium-ion conductivity of 3.35×10-7 S/cm. The films were then annealed, and the effect of annealing on the optical and electrical properties of the films was examined. After annealing at 1000 °C, the films were found to be cubic with a narrower band gap of 3.64 eV. In addition, these annealed films showed an inferior ionic conductivity than the as-deposited ones.

It is well known that tungsten tri-oxide (WO3) exhibits electrochromic and gasochromic properties. When Pt-nanoparticle-dispersed tungsten oxide (Pt-WO3) is exposed to hydrogen gas, the optical and electrical properties of the Pt-WO3 change drastically. Consequently, it is expected that thin films of WO3 can be applied as hydrogen gas leakage sensors. In this study, thin films of Pt-WO3 were prepared on glass substrates using a sol-gel process. The optical and electrical properties of the films were evaluated. Amorphous and crystalline WO3 were easily obtained by changing the heat-treatment temperature. The ion diffusion coefficient of the film depended on the WO3 structure (i.e., whether it was amorphous or crystalline) because the density of amorphous WO3 is lower than that of crystalline WO3. Films with low crystallinity were found to have superior chromic properties to both those with high crystallinity and amorphous films. Thin films of Pt-WO3 prepared at 673K showed the largest change in optical transmittance and electrical conductivity when exposed to H2 gas compared with thin films prepared at other temperatures. When this film was exposed to 100% H2 gas, the normalized transmittance decreased rapidly (in less than 0.2 sec) from 100% to almost 50%. The optical absorbance of the film was dependent on the H2 gas concentration (mixed with N2 gas) in the range from 0.1 to 5% and the relationship between them was linear. The relationship between the electrical conductivity and hydrogen gas concentration (mixed with N2 gas) in the range from 100 to 10000ppm was also linear.

Nanocomposites formed by ferrimagnetic and ferroelectric materials are multiferroic material in which magnetoelectric coupling occurs via piezoelectricity and magnetostriction phenomena. These nanocomposites have a variety of applications in tunable microwave devices using electric control of spin wave propagation or new magnetic memories in which the magnetic response is controlled by electric field.In this work, transparent and homogeneous thin films of barium titanate interleaved with cobalt ferrite were prepared by sol–gel method using dip-coating process. Films of pure barium titanate and cobalt ferrite were also prepared for comparison. The nanocomposite films were deposited onto clean quartz substrates, where a coating of each material was deposited interleaved, where the cobalt ferrite film formed the last layer. The films were dried in air after each dipping and heated at 900 oC for 1 hour to convert the amorphous films into crystalline ones. The samples were characterized by low angle X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) and UV-Vis spectroscopy.

Amorphous films of Ge1-xTex (x=0.37, 0.51, 0.64) prepared by sputtering, by melt quenching or by ion irradiation were annealed up to 450°C. Different phase stability, i.e. crystallization temperature, was observed varying the amorphous status in stoichiometric and Te-rich alloys while no variation was obtained in the Ge-rich alloy. Laser and ion irradiated stoichiometric alloy exhibits lower stability with respect to the sputtered film while irradiated amorphous Te-rich samples are more stable than the as deposited amorphous sample. An enhancement of edge-sharing GeTe4 tetrahedra Raman signal at the expenses of Ge-rich tetrahedra signal occurs in the irradiated samples with respect to the as-deposited amorphous layers both in the stoichiometric and in the Te-rich alloy. The crystallization temperature decreases in GeTe since the system during irradiation is promoted to a state closer to the crystalline phase while in Te-rich alloy the stability increases with the density of Ge-Te bonds since this local rearrangement delays Te precipitation and the subsequent GeTe crystallization. Irradiation does not affect the stability of Ge rich alloy in which crystallization is limited by the Ge mobility and the induced local rearrangements is probably prevented by the low atomic diffusivity.

Silicon nanocrystals with diameters up to 30 nm are used as nucleation seeds for fast solid phase crystallization of amorphous silicon films. Purely amorphous films required an incubation time of up to 12 hours at 600°C prior to the onset of nucleation, while films with nanocrystals embedded between layers of amorphous silicon grew immediately upon annealing in a quartz tube furnace. Structural characterization was performed by heated-stage transmission electron microscopy and Raman spectroscopy.

Silicon-germanium (Si1−xGex:H) thin films have been prepared by plasma enhanced chemical vapor deposition of SiH4 and GeH4 and measured during growth using real time spectroscopic ellipsometry. A two-layer virtual interface analysis has been applied to study the structural evolution of Si:H films prepared in multistep processes utilizing alternating intermediate and low H2-dilution material layers, which have been designed to produce predominately amorphous films with a controlled distribution of microcrystalline particles. The compositional evolution of alloy-graded a-Si1−xGex:H has been studied as well using similar methods. In each case, depth profiles of microcrystalline content, fμc, or Ge content, x, have been extracted. Additionally, real time spectroscopic ellipsometry has been used to monitor post-deposition exposure of a-Si:H, a-Si1−xGex:H, and a-Ge:H films to a hydrogen plasma in situ in order to determine sub-surface amorphous film modification similar to that which would occur when a highly H2-diluted layer is deposited on a layer prepared with lower dilution. These analyses provide guidance for enhanced performance of Si:H based solar cells, through controlled bandgap grading using compositionally graded amorphous binary alloys (a-Si1−xGex:H) or the incorporation of controlled fractions of microcrystallites into bulk amorphous i-layer materials, and by providing a fundamental understanding of the modification of component layers during the deposition of subsequent layers in multilayer stacks.

Epitaxial BiFeO3 (BFO) thick films were fabricated on SrTiO3 (STO) substrates by a simple liquid-phase epitaxy (LPE) growth technique. To avoid the evaporation of Bi, in this process, we used the lid substrate. As starting materials, we used calcined powder or amorphous films deposited by pulsed laser ablation. The fabricated films were found to have a single perovskite phase and be (100)-oriented. Cube-on-cube epitaxial growth of film on the STO substrate was also confirmed by ϕ-scan measurements. The films grown on the substrate display a multigrain structure with a maximum in-plane size of approximately 100μm, and the film thickness was about 3-35 μm. The interface structure between the film and the substrate was relatively smooth. These results indicate that the proposed simple LPE technique is highly suitable for the fabrication of BFO thick films.

Triruthenium dodecarbonyl and trimethylphosphine or triphenylphosphine, and cis-ruthenium(II)dihydridotetrakis-(trimethylphophine) were used in flowing hydrogen or argon at 575 K to explore the effect of changing the percentage of P on the amorphous character of the films and on the electrical properties of the films. First-principles density-functional calculations are presented that reveal the interaction of Ru with P, and that predict the amorphous structure should be most stable above 20 at.% P and 10 at.% B. The films contained a carbon impurity that depended on the delivery gas and the alkylphoshphine source; film resistivity was highly dependent on the carbon impurity level. The microstructure changed with the percentage P; amorphous films formed provided the percentage of P exceeded 15 at.%. Film resistivity was most sensitive to the carbon impurity and also changed with microstructure. A 15 nm thick, amorphous film containing ∼15 at.% P had a resistivity of 210 μohm-cm.

Hydroxyapatite (HA) is a calcium phosphate mineral analogous to the mineral part of bone. This similarity makes this material bioactive and suitable to coat medical implants. However, at present, there is not a coating technique which gives the coated implant the desired properties and long life required for medical implants.In an effort to produce HA coatings with improved properties, calcium phosphate films were prepared using magnetron sputtering deposition on a silicon substrate at 600°C. Initial efforts resulted in the deposition of amorphous films with a distinctive grain-like surface morphology. The morphological grain size was studied using SEM and found that it was possible to control the average diameter value of the round shaped grains by adjusting the deposition time. Increasing the deposition time increases the mean grain diameter. EDS spectra showed the unintentional addition of carbon, iron and nickel to the samples during deposition. After eliminating the impurities, it was possible to prepare calcium phosphate films in the HA phase but without the grain-like surface morphology. These results suggested that the impurities prevented the formation of the calcium phosphate HA phase while acting as nuclei for the heterogeneous nucleation of the grains. This is an important result where the deposition process parameters can be controlled to functionalize the films in order to produce distinctive nanoscale features in the surface morphology.

Phase composition and electrical properties of Ag(Tl)SbS amorphous films obtained by pulse laser deposition technology are investigated. The films deposited on crystalline NaCl and Kcl substrates are amorphous with crystalline phase inclusions. Room-temperature current voltage characteristics showed a good electro-sensitivity of the films under applied bias up to 10 V and a space-charge-limited current was registered as a principal component of the charge carrier transport.

We report a novel class of emitting materials for use in the organic light-emitting devices (OLEDs): multifunctional phosphorescent dendrimers that have a phosphorescent core and have charge transporting dendrons. We have synthesized first-generation and second-generation dendrimers consisting of a fac-tris(2-phenylpyridine)iridium [Ir(ppy)3] core and hole transporting phenylcarbazole-based dendrons. Smooth amorphous films of these dendrimers were formed by spin-coating them from solutions. The OLEDs using the dendrimer exhibited bright green or yellowish-green emission from the Ir(ppy)3 core. The external quantum efficiency of the OLED using the mixture film of the first-generation dendrimer and an electron-transporting material was as high as 7.6%.

TiO2 anatase thin films with different thickness (100 – 1200 nm) have been deposited on glass, sapphire and Si(100) substrates using pulsed DC magnetron reactive sputtering. The thin films were exposed to carbon monoxide (CO) gas at different concentrations (20–100 ppm) in a nitrogen carrier, and the resistance was measured as a function of the CO concentration for films of different thicknesses for temperatures in the range of (100 - 300°C). The films with good crystalline order showed better response than amorphous films. The response increased monotonically with CO concentration. The thicker films showed higher sensitivity. The anatase films deposited on sapphire generally had a larger response than those deposited on glass or on silicon. The films on sapphire substrate showed good response at temperatures as high as 300°C, while those deposited on glass and silicon had good responses only to 200°C. Furthermore, the addition of different concentrations of O2 and H2 affected the response as expected. The response to CO in the presence of N2 showed good reversibility which is evidence that complete regeneration on turn off the CO does not require exposure to oxygen or air. The response and the recovery times are fast.

Glasses rich in rare-earth ions have attracted a lot of interest due to their applications in optical isolators and optical amplifiers. Integrating optical isolators with various optoelectronic devices allows sources to be integrated with lower costs, easier alignment and longer lifetimes. Glasses rich in rare-earth ions have large Verdet constants, so large Faraday rotations. Among the rare-earth ions used in paramagnetic glasses, Tb3+ ions have largest Faraday rotation per ion and the glasses are transparent down to 1.6um. These glasses can also avoid the temperature incompatibility and lattice match problems which are encountered when magneto-optical garnets mare used for integration. The Tb3+doping is also widely used in optical amplifiers. In this paper we have explored the metastable phases present in the sputtered Tb-Al-Si-O system in order to fabricate paramagnetic films with the highest possible Faraday rotations, lowest optical losses and that are easily integrated with semiconductors. A broad peak was observed in the microdiffraction pattern around 2θ= 30deg. This peak corresponded with the close-packed Tb-O plane spacing (111 for FCC Tb4O7 or 002 for HCP Tb2O3), but it was an “amorphous” peak with a 5 deg FWHM. Amorphous films were obtained even when the Tb concentrations were very high. Since high concentrations of Tb are known to devitrify glasses, the discovery of a high-Tb concentrated glass is exciting.

SrTa2O6 thin films with thickness between 6 and 150nm were deposited in a multi-wafer planetary MOCVD reactor combined with a TRIJET® liquid delivery system using a single source precursor, strontium-tantalum-(methoxyethoxy)-ethoxide dissolved in toluene. A rather narrow process window for the deposition of stoichiometric SrTa2O6 was found for this precursor at low pressures and a susceptor temperature around 500°C. Films were grown on Pt/TiO2/SiO2/Si, TiNx/Si, and SiO2/Si substrates. The as-deposited films were X-ray amorphous and could be crystallized by post-annealing at a temperature ≥700°C. The SrTa2O6 phase was dominating within a broad range of compositions (Sr/Ta: 0.4–0.7) and a perovskite type phase was observed for Sr/Ta > 0.7. The electrical properties have been investigated with MIM and MIS capacitors after sputter deposition of Pt top electrodes. The amorphous films had a relative permittivity, ε, in the range of 25–45, and low leakage currents. Crystallized films were investigated with Pt MIM capacitors. For stoichiometric SrTa2O6 the dielectric permittivity reached values of ε = 100–110, but the leakage currents were increased. Remarkably, the permittivity is not very sensitive to deviations from the exact stoichiometry of the SrTa2O6 phase (Sr/Ta: 0.40.7), but a decrease to values of ε = 30–40 is observed along with the phase transition at high Sr contents.

When deposited at room temperature, sputtered NiTi thin films are amorphous and need to be crystallized before they can be used as a functional material. We present the results of an annealing study on substrate-constrained NiTi shape memory thin films. Amorphous films of a NiTi shape memory alloy were deposited by UHV sputtering. Films of thickness 1.0 μm were grown on (100) Si wafers both with and without an LPCVD SiNx barrier. The as-deposited films were annealed in vacuum at temperatures ranging from 500°C to 800°C. The microstructure of the annealed films was characterized using transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and Rutherford back scattering (RBS).

The excess Sb effect for the dynamics of rapid crystallization in eutectic amorphous films are discussed. This crystallization mechanism describe the propagation with high velocity in the interface separating the crystalline and amorphous phase for InSb and AgInSbTe materials. From these analysis, it is clear that the crystallization is grown up in the boundary of crystalline-amorphous region of eutectic materials, which is different from the stoichiometric GeSbTe media. Also, the quantum effect on the melting, crystallization and solidification of phase change media has been discussed.

Photocrystallization is a phenomenon whereby an amorphous matrix undergoes structural changes to micro- or nano-crystals upon irradiation with photons. Topologically, a crystalline phase embedded in an amorphous matrix is expected to be advantageous over a fully crystalline phase, in applications such the as cathode material in thin film lithium-ion rechargeable batteries. As this particular microstructural feature provides a high surface area and enables smooth contacts, it may be expected to result in fast ion conduction between cathode and electrolyte, while retaining the electrochemical property associated with the specific crystal structure of the material. Amorphous films of lithium- incorporated cobalt oxide were obtained on glass and aluminium substrate using a sol gel spin-coating technique. The photocrystallization and microstructural changes in these films upon irradiation with unpolarised light were investigated using XRD, SEM, and TEM analysis.

As gate oxide thickness decreases, the capacitance associated with the depleted layer in polysilicon gate becomes significant, making it necessary to consider alternative gate electrodes. Titanium nitride (TiN) films elaborated with TiCl4 precursor is widely studied as metal gate in semi-conductor technology. In this work, a study of TiN metal gate deposited by MOCVD using TDMAT (Tetrakisdimethylamino titanium) precursor is proposed. N2, H2 plasma application and SiH4 treatment after TiN thin film growth modify composition and microstructure. Consequently, they alter the physical properties of films. Such treatments may be a way to modulate work function and thus to control threshold voltage.Metallic layers were deposited in a chamber using a commercial 8 inch wafer deposition tool. In this study, structural and compositional properties of TiN were correlated with work function measurements. Firstly, the composition evolution (carbon content) was studied by AES and SIMS as a function of plasma and SiH4 treatments; XRD gave details on the microstructure. Secondly, MOS structures were processed on uniformly p-type doped wafers. C-V curves of capacitors were used to estimate the flat band voltage (VFB) and gave access to the work function, the effect of oxide fixed charges and the density of interface states. It is shown that as-deposited amorphous films exhibit a work function of 4.4 eV. Exposure to SiH4 is shown to increase this work function of about 150 meV. Thin films properties are not impacted by anneal treatments. Work function stability was tested at 425 °C, 900 °C and 1050 °C. Thermodynamic compatibility with gate oxide was verified thanks to experimental results and calculations.

The growth front roughness of Ta2O5 amorphous films grown by pulsed plasma d.c. reactive sputtering has been investigated using atomic force microscopy. Film deposition during reactive sputter deposition is explained based on dynamic scaling hypothesis in which both time and space scaling are considered simultaneously. The interface width w increases as a power law with deposition time t, w ∼ tβ, with β = 0.45 ± 0.03. The lateral correlation length ξ grows as ξ ∼ t1/z, with 1/z = 0.61 ± 0.07. The roughness exponent extracted from the slope of height-height correlation analysis is α = 0.79 ± 0.04. The results are similar to that obtained by sputtering of elemental materials, and do not fit to any of the presently known growth models. Monte Carlo simulations were carried out based on a recently developed re-emission model, where incident flux distribution, shadowing, sticking coefficient, and surface diffusion mechanisms were accounted for in the deposition process. An important finding is that sticking coefficient must be less than unity to obtain the observed β value (∼0.45).

Amorphous and microcrystalline silicon films were deposited by HWCVD under different deposition conditions and the gas phase chemistry was studied by in situ Quadrupole Mass Spectrometry. Attempt is made to correlate the properties of the films with the gas phase chemistry during deposition. Interestingly, unlike in PECVD, partial pressure of H2 is higher than any other species during deposition of a-Si:H as well as μc-Si:H. Effect of hydrogen dilution on film properties and on concentration of various chemical species in the gas phase is studied. For low hydrogen dilution [H2]/ [SiH4] from 0 to 1 (where [SiH4] is 10 sccm), all films deposited are amorphous with photoconductivity gain of ∼ 106. During deposition of these amorphous films SiH2 was dominant in gas phase next to [H2]. Interestingly [Si]/[SiH2] ratio increases from 0.4 to 0.5 as dilution increased from 0 to 1, and further to more than 1 for higher hydrogen dilution leading to [Si] dominance. At hydrogen dilution ratio 20, consequently films deposited were microcrystalline.

Chemical-vapor-deposition of titanium tetra-isopropoxide (TTIP) under the atmosphere at low temperature has been conducted. The structure of the obtained films was assessed using Fourier transform infrared spectroscopy, X-ray diffractometry and Raman spectroscopy. These analyses indicated that amorphous TiOxHy films were obtained at gas temperatures in the range of 150–300 °C, and crystalline anatase-TiO2 film was formed at 350 °C. This distinction is accounted for by plausible chemical reactions as follows; the hydroxyl reaction of TTIP below 350 °C promotes the formation of the amorphous TiOxHy. As the temperature goes up to 350 °C, dehydrogenation of the TiOxHy films promotes to form crystalline TiO2. Also the obtained amorphous films were annealed for 10 min under the atmosphere in assessing the transformation proceeding in the solid state. The structural change is shown at 350 °C, indicating that the crystalline phase would be formed via dehydrogenation and polymerization on the surface of the amorphous phase under the atmosphere. The crystal size of the annealed films was evaluated in assessment for the transformation.

A metal-free germanium-induced crystallization technique is reported to realize poly-silicon films on glass at temperatures as low as 480°C. The reduction in crystallization temperature is achieved by using ultra-violet illumination during thermal treatment of the amorphous silicon layer. The annealed samples have been studied using SEM and XRD analyses. Also the electrical conductivity of samples with various annealing conditions has been examined. Conductivity of the samples annealed in the presence of ultra-violet exposure shows more than three orders of magnitude improvement compared to that of amorphous films. Samples treated without UV exposure do not show much enhancement. Size of poly-silicon grains is 0.3μm, as revealed using SEM study.

Fracture behavior of micro-sized cantilever beam type specimens prepared from an electroless deposited Ni-P amorphous alloy thin film has been investigated at ambient and elevated temperatures. Cantilever beam type specimens with dimensions of 10 x 12 x 50 μm3 were prepared from an electroless deposited Ni-P amorphous alloy thin film and notches were introduced by focused ion beam machining. Fatigue pre-cracks were introduced ahead of the notches. The introduction of fatigue pre-crack and fracture toughness tests were carried out using a mechanical testing machine for micro-sized specimens. The temperature of the specimen was controlled from room temperature to 473 K using a newly developed heating system. Compared with room temperature, fracture toughness increased approximately 40 % at 373 K but decreased 19 % at 473 K. The increase of fracture toughness at 373 K is considered to be related with the formation of nano-sized crystals and the decrease of fracture toughness at 473 K is considered to be due to the growth of crystals. It is required to consider the fracture behavior obtained in this investigation when designing actual MEMS devices using electroless deposited amorphous films.

Thin films of TiNi shape memory alloy (SMA) have been prepared by pulsed-laser deposition (PLD) at different substrate temperatures. The stoichiometry, crystallinity, and morphology of the deposited films were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atom force microscopy (AFM). The transformation behavior and crystallization temperatures were investigated by differential scanning calorimetry (DSC). It is found that the Ni content of the deposited films ranges from 46.7 to 52.0 at.%. The crystallization temperature of the amorphous films is around 460°C. The activation energy of the crystallization process is determined by Kissinger's method to be 301 kJ/mol. The martensitic transformation temperature of the annealed Ti-51.5 at.% Ni film is –20.8°C.

Laser based crystallization of thin amorphous films on glass substrates have entered into industrial applications since several years. The excimer laser based process provides a low temperature procedure to obtain polycrystalline silicon films on flat panel display substrates to fabricate thin film transistors (TFT's).The key to this application is a uniform illumination of the. Line Beam systems provide up to 365mm long homogeneous exposure fields operated with up to 300 W average power 308nm excimer lasers. The paper covers a technical overview of Line Beam Optics layout, recent developments and results.Further high resolution optics are described and discussed for sequential lateral solidification (SLS) (1,2,3) processes. The SLS application has demonstrated to efficiently produce directionally solidified microstructures or even grain-boundary –free regions on Si-films. Diffraction limited resolution in the range of several micrometers and high optical throughput are important parameters to this application.General considerations are presented to describe technical limits which compromise laser beam related coherence effects, optimum uniform illumination, adequate resolution and depth of focus and optical efficiency for the practical application.

Nd doped TiO2 nanostructured thin films were prepared by sol-gel technique on quartz and Si substrates using TiCl4 precursor. As-deposited amorphous films were annealed to form anatase phase in the thin films. The film grain size increased with annealing temperature. Above 800°C, rutile began to segregate and the grain size decreased slightly.The photodegradation of 2-chlorophenol (2-CP) was studied. Doping TiO2 with Nd+3 reduced the photodegradation time. The difference in the ionic radii of Nd+3 and Ti+4 and the oxygen affinities of Nd and Ti were responsible for this effect. These differences help promote electron trapping, thereby increasing the lifetime of the holes which are responsible for the oxidation of 2-CP.

Thin amorphous films of tantalum oxide were grown on borosilicate crown glass substrates by KrF excimer pulsed laser ablation of a Ta2O5 target, in an oxygen environment. The deposition was performed at a temperature of 250 or 400 °C, while the oxygen pressure was set in the range 5 to 30 mTorr. The optical properties of the tantalum oxide coatings, as evaluated by reflectance/transmittance spectrophotometry, were found to be dependent on the oxygen gas pressure. At a pressure of 5 mTorr, absorbing films were obtained, with extinction coefficients above 10−2 (at λ=633 nm), along with an optical energy band-gap as low as 0.7 eV. At a pressure of 10 mTorr and above, the coatings had refractive indices up to 2.25 (at λ=633 nm), extinction coefficients below 10−4 (for λ>390 nm), and an optical energy band-gap in the range 3.9 to 4.0 eV.

A novel pattern transfer technique, based upon direct contact between nanofabricated printheads and amorphous films/substrates is being developed. Transfer of features from printhead to substrate is via an induced crystallization mechanism, with a goal of controlling crystal nucleation at dimensions comparable to the printhead features. To realize such a printing mechanism, appropriate mediums/materials that can be crystallized through contact with the printhead elements must be identified. From a range of candidate materials we focus on Ge and Indium Tin Oxide (ITO) films grown by molecular beam epitaxy or sputtering. The crystallization may be induced directly by heating (thermally), pressure (mechanically), or electrical conduction through the contact points. Crystallization of many amorphous materials is known to be self sustaining (so called “explosive crystallization”), raising the need to identify mechanisms for abruptly stopping crystallization if feature dimensions are to be constrained. A set of amorphous or nanocrystalline samples have been studied during crystallization by a heated printhead fabricated with a Focused Ion Beam (FIB). A simplified continuum model suggests the feasibility of achieving lateral confinement of the induced crystallization. In order to characterize fully the transitional and final substrate states, real-time observation of nanoscale crystallization in the transmission electron microscope (TEM) is in progress. A special TEM goniometer is being developed which incorporates a piezoelectrically driven tip and a heating capability to enable observation of tip-substrate contact at elevated temperatures that should give invaluable insight into crystallization mechanisms.