In order to study mechanism of laser ablation, the time-of-flight spectra of monovalent ions generated by ablation of alkaline earth metals are measured. The obtained spectra show that the ion generation is caused by 5-, 4- and 3-photon processes for Ca, Sr and Ba, respectively, when ArF excimer laser is used as a light source. This behavior suggests that laser ablation of alkaline earth metals is triggered by excitation of electrons at the highest inner-core level. Control of layer-by-layer growth processes by monitoring emission from the ablation plume is also reported. The emission measurement is utilized for estimation of each layer thickness in layer-by-layer growth. This conventional technique is very effective for automatic control of layer-by-layer growth.

We provide evidence that non-stoichiometric ablation of YBa2Cu3O7δ at low fluences is due to a phase separation of the target surface. On the other hand, in SrTiO3 we find at low fluences evidence for preferential ablation which is assisted by volume-diffusion. As a result, the Sr/Ti ratio of the ablated films can be tuned by choosing the appropriate fluence.

We are reporting the successful deposition of single phase c-axis oriented ferroelectric thin films of PbTiO3 on Si (100) by pulsed laser deposition. It is shown that the formation of non ferroelectric Pb2Ti2O6 phase at the interface could be avoided by raising the substrate temperature sufficiently high. The film deposition conditions are optimized so as to achieve better ferroelectric properties.

Film growth in pulsed laser deposition (PLD) is described as a process of sorption of ablated species on the substrate surface. Film growth rate and composition are qualitatively analyzed as a function of laser fluence and ambient gas pressure. As an example, analysis of the film composition is carried out for BiSrCaCuO and PbZrTiO pulsed laser deposited films.

We have deposited ferroelectric thin films by pulsed laser deposition to be used as an inline optoelectronic modulator utilizing evanescent field coupling to a side-polished optical fiber. In order to satisfy waveguiding conditions, amorphous quartz substrates (n= 1.447) were necessary. Ferroelectric films of (Pb0.91La0.90)(Zr0.65,Ti0.35)O3, Pb0.80La0.20TiO3 (PLZT), and Sr0.5Ba0.5TiO3 were deposited on quartz substrates and thin Bi4Ti3O12 buffer layers were explored as a chemical barrier and to improve crystallographic texturing. The morphology of thick films (˜3 µm) of PLZT was not acceptable for optical applications, whereas the Sr0.5Ba0.5TiO3 films were very smooth, but had some cracking. The Sr0.5Ba0.5TiO3 films were optically determined to be uniform and of sufficient quality for use in fabricating in-line fiber optic modulators.

Thin LiNbO3 films are deposited on (001) sapphire substrates by Ar F pulsed laser ablation. The films are evaluated by X-ray diffraction analysis at various temperatures, as well as high-resolution transmission electron microscopy (TEM). The deposited films are highly epitaxial but that are strained, that is, the a-axis is longer and the c-axis is shorter than those of LiNbO3 single crystals. X-ray diffraction analysis at deposition temperature, as well as TEM show that the strain is caused by the difference in thermal expansion coefficients between LiNbO3 and sapphire substrates.

Amorphous tantalum pentoxide (Ta2O5) and niobium pentoxide (Nb2O5) thin films were grown from both metal and oxide target by reactive pulsed laser deposition. Film structure and composition were studied as a function of substrate temperature and oxygen pressure. Good quality transparent films were obtained for substrate temperatures greater than 140° C, and O2 pressures of 200 mTorr. Lower temperatures and pressures produced opaque films, associated with lower oxides.

A thin film superlattice heterostructure composed of alternating BaTiO3 and SrTiO3 layers was grown on a thin YBa2Cu3O7 electrode templated on a (100) SrTiO3 wafer using the pulsed laser deposition method. Stranski-Krastanov nucleation of the layers was demonstrated using atomic force microscopy (AFM) when processing conditions were maintained at 6 millitorr oxygen partial pressure, and 550 °C substrate temperatures. High-resloution x-ray diffraction (HRXRD) measurements indicate that all the deformation was concentrated in the BaTiO3 layers with c/a extension to approximately 1.08. Rutherford backscattering spectroscopy (RBS) results indicate excellent crystallinity in the heterostructure. The microstructural data suggests that the theoretical critical thickness of the film has been surpassed by an order of magnitude.

Transparent conducting thin films of approximately 1000-2000 Å were deposited on glass, quartz and silicon substrates using standard pulsed laser deposition techniques with two different targets (Sn and SnO2) and with three different laser wavelengths (1.06, 0.532 and 0.266 urn) from a Q-switched Nd:YAG laser. Composite films of SnO2 and Sn with high optical transmission were obtained using a Sn target and a background oxygen pressure of 20 Pa with optical transmission over most of the visible spectrum exceeding 80%. Electrical resistivities of approximately 10-2 Ω-cm were obtained. Using SnO2 targets, predominantly amorphous phase SnO2 films were deposited on Si substrates and then transformed into polycrystalline Sn3O4 by laser induced crystallization (λ = 1.06 μm). The electrical resistivity of these films was also permanently reduced by a factor greater than 1000.

Thin films of poly(tetrafluoroethylene) have been deposited on amorphous (7059 Corning Glass) and silicon(l00) substrates at various temperatures by the Pulsed Laser Deposition technique. The deposition was carried out at high vacuum (˜10-6 torr)at temperatures ranging from room temperature to 350°C. The mechanical properties of these films at the varying process temperatures have been evaluated by nano-indentation techniques and compositional properties of the films have been characterized by Fourier Transform Infrared spectroscopy. The deposition parameters have been optimized in order to produce good quality films.

Recent reports on high transient transverse voltages at room temperature in YBa2Cu3O7 and PrxYl-xBa2Cu3O7 thin films grown on SrTiO3 single crystal substrates, with a tilt angle between the [ 001 ] cubic axis and the substrate surface plane, have been interpreted by thermoelectric fields transverse to a laser-induced temperature gradient which are caused by the non-zero off diagonal elements of the Seebeck tensor. We have studied this effect in epitaxially grown Pr- doped, as well as undoped YBa2Cu3O7, thin films and observed for a 2 mm long YBa2Cu3O7 strip exposed to a UV photon fluence of 100 mJ/cm2 signals as large as 30 V. The unexpected high values for the signals and their doping dependence are discussed within the frame of a model based on a thermopile arrangement, the growth induced defect structure and the doping induced modifications of the material properties.

Ferroelectric SrBi2Ta2U9 (SBT) thin films were synthesized by pulsed laser deposition (PLD) on platinized silicon substrates held at different substrate temperatures, from targets with different compositions. It was necessary to anneal films deposited at low temperature (525°C) at elevated temperatures in an oxygen atmosphere in order to achieve properties comparable to SBT thin films grown by the sol-gel technique. Polarization – electric field hysteresis loops showed saturation in the 2-5 V range with a remnant polarization 2Pr = 8-13 µC/cm2. Capacitors showed negligible fatigue up to 1010 switching cycles.

Microstructural and magnetoresistance properties of La0.6Y0.07Ca0.33MnOx (Y-doped LCMO) thin films grown in-situ by pulsed laser ablation have been studied. Transmission election microscopy and x-ray diffraction measurements have shown that the Y-doped LCMO thin films grow epitaxially on (100) LaAl03 substrates and are cubic with a lattice parameter of 3.849 ?. The as-deposited films exhibited a metal-insulator transition at 130 K and a giant magnetoresistance (GMR) at 125 K with a MR ratio (dR/RH) of 1500% in the presence of a magnetic field of 6 Tesla. Such a colossal value of MR ratio for as-deposited Y-doped LCMO films is quite promising keeping in view the fact that these films were unannealed and not optimized. We ascribe this magnetoresistance to spin-dependent electron scattering coupled with the presence of intervening O2. ions across Mn3+ and Mn4+ with suppressed separation between Mn-O layers caused by smaller sized Y-dopant. The effect of annealing on the positive-shift of metal-insulator transition temperature and the improvement in GMR ratio has also been discussed. We also report a non-ohmic response in the Y-doped LCMO films which is observed only in the region of the resistance peak and lends support to a conduction mechanism in these materials based on spin-dependent scattering of electrons.

Highly transparent with low electrical resistivity gallium-doped zinc oxide (ZnO:Ga) thin films were prepared on glass by Pulsed Laser Deposition at different substrate temperatures. ZnO:Ga evaporation targets were prepared by pressing and sintering powder materials obtained with a novel combustion synthesis technique.

An excellent transmittance of more than 85% in the visible range and a low sheet resistance value as low as 13 Ω/sq. were measured on a 200 nm thickness film grown at Ts=300°C. From optical measurements we observed an increase in the ZnO:Ga bandgap when the substrate temperature is raised from 150°C to 300°C. With this, a remarkable improvement in the blue-green region transmittance is obtained.

X-Ray diffraction patterns indicate that the films grow highly oriented in the basal plane direction (c-axis) of the hexagonal ZnO grains.

Gallium - lanthanum sulphide glasses (GLS) show wide range transparency and low non radiative relaxation rates for dopant ions such as Ho3+, Er3+ etc. They also show permanent photomodification of the refractive index under visible illumination. We report laser ablation deposition of these glasses and preliminary results on film stoichiometry and deposition rate as a function of excimer laser fluence. The sulphur to metal and Ga/La ratios are found to have marked fluence dependencies. The films show considerably more Urbach tail absorption than bulk material. A novel method has been developed for mapping the permanent photomodified index.

We have investigated the growth of GdLiF4 thin films for optical waveguide applications using pulsed-laser deposition (PLD). Epitaxial, c-axis oriented GdLiF4 films have been grown from undoped GdLiF4 targets in an on-axis PLD geometry on (100) CaF2. These films exhibit a high density of particulates on the surface which are ejected from the target in the ablation process. Growth from Nd-doped polycrystalline GdLiF4 ablation targets results in relatively smooth films with lower particulate densities, as Nd doping significantly increases the optical absorption of GdLiF4 at the ablation laser wavelength of 193 nm and permits efficient pulsed-laser deposition. Optical emission spectra of the ablation pume reveals the presence of atomic fluorine, gadolinium, and lithium, indicating the dissociation of the metal-fluorine bonds in the ablation process. In addition, we find that the residual background oxygen pressure must be sufficiently reduced to avoid the formation of Gd4O3F6 as an impurity oxy-fluoride phase in the films.

The probe beam deflection and optical time-of-flight method have been applied to study the dynamics of Nd:YAG laser (266 nm) ablation of pyrolytic boron nitride. Shock wave generation was observed and its velocity was derived by analysis of the acoustic transit time of the acoustic wave produced by laser ablation. The most probable velocities of B and B+ were obtained by optical time-of flight technique. The deposition of boron nitride on silicon substrate by laser ablation was attempted in nitrogen atmosphere. Cubic phase of boron nitride was observed as well as the hexagonal phase.

We have investigated epitaxial growth of TiN on sapphire and electronic grade silicon-on-sapphire (SOS) by PLD. A pulsed KrF excimer laser was used to ablate the stoichiometric TiN target in the deposition chamber maintained at a base pressure of 3xl0-7 Torr. Epitaxial growth was achieved at deposition temperatures of 500-700°C. The films were characterized by x-ray diffraction technique, Raman spectroscopy, high resolution electron transmission microscopy and four-point-probe electrical resistivity. The x-ray diffraction and TEM results showed that the TiN films deposited on sapphire (0001) and SOS above 500oC were single crystal in nature. The epitaxial relationship for TiN on sapphire was found to be TiN[1 1 1]||Al2O3[0001] and in-plane alignment of TiN[110]||Al2O3[1010]. In case of growth on SOS, epitaxy of TiN on Si was cube-on-cube and is similar to that of TiN grown on bulk Si substrates. Four-point-probe electrical resistivity measurements showed characteristic metallic behavior of these films as a function of temperature with the lowest value of resistivity of about 20-22μΩ-cm at room temperature. This paper describes the fundamental issues related to epitaxy, defect formation and nitride-oxide interfaces. It is also shown that the TiN films on sapphire and SOS have unique characteristics and are promising for metallization in advanced microelectronics.

We deposited diamond-like carbon (DLC) films, using frozen acetylene and acetone as the target of laser ablation. The frozen gases were dissociated by an ArF laser and a KrF laser. The DLC films were deposited on quartz substrates below 300°C. We measured the Raman spectra to identify the deposited films as DLC. The films showed the broad Raman peak at 1540 cm-1. The number of particles mixed into the deposits was controlled by laser power densities. By using the ArF laser for frozen acetylene we could reduce the hydrogen concentration in the films, which showed a high degree of dissociation of the source gas. The oxygen content was kept at the same level in the films deposited from frozen acetone as from frozen acetylene. The present results suggested the importance of energetic and charged species ejected from the frozen gas target.

A liquid-target pulsed laser deposition system has been designed to grow diamond and diamond-like carbon films using an organic liquid. The system has overcome the problem of target deterioration under high power laser irradiation and has prevented splashing of large particulares on the substrate. The technique is simple and safe to operate and the cost of source materials is much lower than in chemical vapor deposition experiments. With the introduction of oxygen (O2) gas during deposition, only diamond-like carbon is produced. Crystalline diamond films can be obtained when H2O2 is added along with O2 gas. The results provide a evidence that hydroxyl ions, OH-, together with atomic oxygen can indeed promote diamond growth.