M-thick Film Research Articles

Polymer-coated compliant receivers for intact laser-induced forward transfer of thin films: experimental results and modelling

In this study, we investigate both experimentally and numerically laser-induced forward transfer (LIFT) of thin films to determine the role of a thin polymer layer coating the receiver with the aim of modifying the rate of deceleration and reduction of material stress preventing intact material transfer. A numerical model of the impact phase during LIFT shows that such a layer reduces the modelled stress. The evolution of stress within the transferred deposit and the substrate as a function of the thickness of the polymer layer, the transfer velocity and the elastic properties of the polymer are evaluated. The functionality of the polymer layer is verified experimentally by LIFT printing intact 1- \(\upmu \)m-thick bismuth telluride films and polymeric light-emitting diode pads onto a layer of 12-\(\upmu \)m-thick polydimethylsiloxane and 50-nm-thick poly(3,4-ethylenedioxythiophene) blended with poly(styrenesulfonate) (PEDOT:PSS), respectively. Furthermore, it is demonstrated experimentally that the introduction of such a compliant layer improves adhesion between the deposit and its substrate.

Analytical study of vertical external-cavity surface-emitting organic lasers

In this paper we report a detailed study of emission dynamics of an organic solid-state laser structure so-called VECSOL standing for Vertical External-Cavity Surface-emitting Organic Laser recently developed in our group. An optical-optical efficiency of 43% and 6.3% was reported for a 4-mm-long cavity incorporating 18- μ m-thick film of Poly(methyl methacrylate) (PMMA) doped with 1 wt.% of Rhodamine 640 when pumped with 7-ns-long and 0.5-ns-long pulses respectively. In order to understand the difference seen in lasing efficiency as a function of different parameters such as cavity length or pump pulse duration, Tang-Statz-deMars cavity rate equations are used to model the emission behavior in a pulsed regime. Based on this model, conversion efficiency could be optimized practically to values as high as 57%. Furthermore, some characteristics of this laser architecture such as lasing lifetime (up to 140 000 pulses at two times above lasing threshold), wavelength tuning (over 40 nm) and the system power scalability with potential operation up to mJ level are investigated.

Submicrometer-Thick Low-Loss As$_2$S$_3$ Planar Waveguides for Nonlinear Optical Devices

We describe a fabrication process for and the characterization of submicrometer-thick As <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> waveguides. Poly(methylmethacrylate) and bottom antireflective coating were employed as thin protective layers prior to photoresist patterning in order to prevent the attack of the As <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> film by an alkaline developer. Propagation losses of ~0.2 and 0.6 dB/cm were measured for 4- and 2-¿m-wide waveguides fabricated from 0.85-¿m-thick films. Slightly higher loss in the transverse-magnetic mode may be the result of surface scattering of the rougher etched sidewalls.

The Effect of Film Thickness of Indium-Substituted (Bi3.35Nd0.65)Ti3O12 Films on Ferroelectric Performance

Ferroelectric performance of indium-substituted (Bi 3.35 Nd 0.65 )Ti 3 O 12 (In-BNdT) films prepared by chemical solution deposition was evaluated at different film thicknesses. In-BNdT films crystallized at 650°C had bismuth-layered perovskite structure. Electrical properties were dependent upon the film thickness. Thinner 0.25 μ m-thick In-BNdT films displayed a saturated hysteresis loop, but the effect of their defect-associated interfacial layer became apparent, which led to faster relaxation degradation and a higher leakage current density. The 0.25 μ m-thick films had remanent polarization P r of 38 μ m/cm 2 and coercive field E c of 97 kV/cm at an applied voltage of 8V, dielectric constant of 263, and dielectric dissipation of 0.20.

PREPARATION AND PROPERTIES OF LITHIUM-DOPED K0.5Na0.5NbO3 THIN FILMS BY CHEMICAL SOLUTION DEPOSITION

ABSTRACT Lithium-doped K0.5Na0.5NbO3 (KLNN) films were fabricated by chemical solution deposition on Pt/TiO2/SiO2/Si substrates. Homogeneous and stable precursor solutions were prepared by controlling the reaction of starting metal alkoxides. Perovskite KLNN single-phase thin films were successfully synthesized on Pt/TiO x /SiO2/Si substrates. The 0.75-μ m-thick KLNN film annealed at 650°C exhibited ferroelectric polarization hysteresis loops at −250°C. The loop at room temperature was round, indicating the film contained leakage components. The dielectric constant under zero bias was 490 at room temperature. A typical upside-down butterfly DC bias-capacitance curve was obtained in the KLNN film capacitors at room temperature, indicating that polarization reversal occurred in the obtained KLNN films.

CHARACTERISTICS OF PIEZOELECTRIC MICRO-SPEAKER FABRICATED WITH ZNO THIN FILM

ABSTRACT A piezoelectric microspeaker was fabricated on the 5 × 5 mm2 diaphragm with highly c-axis oriented ZnO thin film on a heavily compressive-stressed silicon-nitride film. Four masks were used in the fabrication processes of the piezoelectric microspeaker. 0.5 μ m-thick piezoelectric ZnO film was deposited by RF-magnetron sputtering method on an Al bottom electrode. Then, 0.2 μ m-thick Al film was deposited for the top electrode. To enhance the ZnO film quality for improving the microspeaker performance, two-step deposition technique was adopted. The back-side silicon nitride was patterned, and silicon substrate was removed to make a diaphragm. The speaker output pressure level (SPL) of the fabricated microspeaker was measured with the variation of sinusoidal input frequency and compared to that of the commercial piezo-ceramic speaker. The largest SPL of the microspeaker was about 92 dB at the input voltage of 6Vpeak-to − peak, which was measured at the distance of 3 mm from the microspeaker in open field. The SPL of microspeaker was nearly same as that of a commercial piezo-ceramic speaker.

Synthesis and Characterization of Bifunctional Organic-Glasses Based on Diphenylhydrazone and Barbituric Acid Derivative for Photorefractive Application

A series of amorphous molecules that possess both photoconductive and electro-optic properties was synthesized in order to investigate photorefractive properties of bifunctional organic-glasses. Diethylaminobenzaldehyde-diphenylhydrazone was covalently attached to 5-(4-diethylamino-benzylidene)-1,3-dimethylpyrimidine-2,4,6-trione through a flexible alkyl chain (3, 4, 5, 6 and 10 carbons) containing two ether linkages. The longer linkage not only lowered the glass transition temperature (<TEX>$T_g$</TEX>) of the molecules, but also allowed faster orientation of the chromophore. To examine the photorefractive properties, a 50 <TEX>${\mu}$</TEX>m-thick film was prepared from the mixture of a bifunctional molecule, butyl benzyl phthalate, and <TEX>$C_{60}$</TEX>. The photoconductivity of this composite was as high as <TEX>$8.01\;{\times}\;10^{-12}$</TEX> S/cm at 60 V/ <TEX>${\mu}$</TEX>m, and the maximum diffraction efficiency ( <TEX>${\eta}_{max}$</TEX>) of 50 <TEX>${\mu}$</TEX>m-thick film was about 5% at 80 V/ <TEX>${\mu}$</TEX>m.

Phase Development and Electrical Properties of Pb(Yb 1/2 Nb 1/2 )O 3 -PbTiO 3 Epitaxial Films

The growth and electrical properties of Pb(Yb 1/2 Nb 1/2 )O 3 -PbTiO 3 (PYbN-PT) epitaxial films were investigated. PYbN-PT epitaxial films with SrRuO 3 bottom electrodes were grown by pulsed laser deposition. Optimization of the growth conditions for the PYbN-PT epitaxial films was carried out on (100) SrRuO 3 /(100) LaAlO 3 substrates using the (50/50) composition target. It was found that formation of pyrochlore phase could be caused not only by low growth temperatures or lead deficiency, but also by poor surface condition of the SrRuO 3 bottom electrodes. (001) PYbN-PT epitaxial films with good crystalline quality were obtained for a range of deposition rates (60-100 nm/min) and temperatures (620-680 °C) after vacuum annealing the SrRuO 3 bottom electrodes. The ferroelectric and piezoelectric properties of 1 w m-thick PYbN-PT epitaxial films with (50/50) and (60/40) compositions and with (001) and (111) orientations were investigated using (100) LaAlO 3 , (100) SrTiO 3 , and (111) SrTiO 3 substrates with SrRuO 3 bottom electrodes. The highest remanent polarization (29 w C/cm 2 ) and effective piezoelectric coefficient e 31.f ( m 14 C/m 2 ) were observed in the (001) PYbN-PT (50/50) film. The transition temperature of the (001) PYbN-PT (50/50) film was about 380 °C. Because of the degradation of the target during the deposition, a 3 w m-thick film was prepared by three depositions (1 w m each layer). The 3 w m-thick film exhibited a higher e 31.f coefficient of m 19 C/m 2.

Free-carrier and phonon properties ofn- andp-type hexagonal GaN films measured by infrared ellipsometry

Infrared spectroscopic ellipsometry (IRSE) over the wave-number range from 300 to 1200 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ is used to determine the anisotropic room-temperature optical properties of highly resistive, Si-doped n-type and Mg-doped p-type \ensuremath{\alpha}-GaN. The approximately 1-\ensuremath{\mu}m-thick films were deposited on c-plane sapphire by molecular beam epitaxy without a buffer layer. The free-carrier concentrations are obtained from Hall measurements. The IRSE data are analyzed through model calculations of the infrared optical dielectric functions parallel (\ensuremath{\parallel}) and perpendicular (\ensuremath{\perp}) to the c axis of the \ensuremath{\alpha}-GaN films. We obtain the thin-film phonon frequencies and broadening values and the optical mobility and effective-mass parameters for n- and p-type \ensuremath{\alpha}-GaN. In agreement with Perlin et al. [Appl. Phys. Lett. 68, 1114 (1996)] we determine the effective electron masses as ${m}_{e,\ensuremath{\perp}}{/m}_{0}=0.237\ifmmode\pm\else\textpm\fi{}0.006$ and ${m}_{e,\ensuremath{\parallel}}{/m}_{0}=0.228\ifmmode\pm\else\textpm\fi{}0.008.$ For p-type GaN with hole concentration ${N}_{h}=8\ifmmode\times\else\texttimes\fi{}{10}^{17}{\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ we find ${m}_{h}{/m}_{0}=1.40\ifmmode\pm\else\textpm\fi{}0.33,$ which agrees with recent theoretical studies of the Rashba-Sheka-Pikus parameters in wurtzite GaN. However, no substantial anisotropy of the effective hole mass is obtained to within 25%. The ellipsometry data also allow for derivation of the model quantities ${\ensuremath{\epsilon}}_{\ensuremath{\infty},j}$ $(j=\ensuremath{\perp},\ensuremath{\parallel}),$ which are almost isotropic but may vary between 4.92 and 5.37 depending on whether the films are undoped or doped. In heavily-Si-doped n-type \ensuremath{\alpha}-GaN we observe a thin carrier-depleted surface layer and additional infrared-active vibrational modes at 574, 746, and 851 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. Raman measurements of the GaN films are also performed, and the results are compared to those obtained from the IRSE investigations.

Electrical properties of Y1Ba2Cu3Ox films grown by liquid phase epitaxy

Abstract Y 1 Ba 2 Cu 3 O x films were grown on MgO(100) substrates by liquid phase epitaxy and their structural and electrical properties were examined. From transmission electron microscopy (TEM) plan-view images, it was found that the films consisted of large grains whose misorientation angles were less than 1°. Although d.c. critical current density values decreased with increasing film thickness, even a 7 μ m-thick film showed the value of 9×10 5 A/cm 2 at 77 K. An rf first penetration field of the film is estimated to be 30 Oe at 10.8 GHz and 77 K, by using a microstrip line resonator with a resonant frequency of 10.8 GHz. The third-order intercept point of the resonator is at an input power of +43 dBm and output power of +30 dBm at 77 K. These results suggest that LPE grown Y 1 Ba 2 Cu 3 O x films have superior d.c. and rf electrical properties.

Spin-wave instability magnon distribution for parallel pumping in yttrium iron garnet films at 9.5 GHz

Parallel-pumping spin-wave instability processes for 2-, 4.15-, and 6-\ensuremath{\mu}m-thick yttrium iron garnet films have been studied by microwave and Brillouin light-scattering techniques. The pump frequency was 9.5 GHz. The static and linearly polarized microwave fields were in plane. Butterfly curves of the instability threshold microwave-field amplitude vs the static field H were measured, along with companion determinations of the critical mode in-plane spin-wave polar-angle ${\mathrm{\ensuremath{\theta}}}_{\mathrm{k}}$ and in-plane wave-number k distributions vs H. The 4.15- and 6-\ensuremath{\mu}m-thick films show narrow distributions in the critical-mode ${\mathrm{\ensuremath{\theta}}}_{\mathrm{k}}$ values and broad distributions in the critical-mode k values which appear at threshold and extend to high power. For the 2-\ensuremath{\mu}m film, the critical-mode ${\mathrm{\ensuremath{\theta}}}_{\mathrm{k}}$ distribution is narrow just at the instability threshold. As the power is increased, the critical-mode ${\mathrm{\ensuremath{\theta}}}_{\mathrm{k}}$ distribution broadens and develops a bimodal character indicative of a splitting into two critical modes. These distributions also show considerable fine structure. The basic shape of the butterfly curve and the measured ${\mathrm{\ensuremath{\theta}}}_{\mathrm{k}}$ values for the 4.15- and 6-\ensuremath{\mu}m-thick films are in rough agreement with predictions from bulk theory, except that the measured k values are in the ${10}^{4}$ rad/cm range rather than near zero. These measured k distributions are quite broad and also show significant structure.

Investigation of a High Quality and Ultraviolet-Light Transparent Plasma-Enhanced Chemical Vapor Deposition Silicon Nitride Film for Non-Volatile Memory Application

A high quality and ultraviolet-light transparent (UV-transparent) plasma enhanced chemical vapor deposition (PECVD) silicon nitride ( SiNx ) film is developed to form passivation layer for non-volatile memory devices. Comparing to the conventional PECVD SiNx film known to have tensile stress and opacity to ultraviolet-light (UV-light), the proposed SiNx film with very low compressive stress ( <1×109 dyn/cm2) and excellent UV-transmittance (>70% for 1.6 µ m-thick film) can be achieved. The film stress is strongly related to RF input power during deposition process. The UV-transmittance is influenced by pressure and SiH4/NH3 flow ratio. It is also shown that the UV-transmittance is closely correlated to refractive index (RI), film density as well as N/Si ratio inside the film. This SiNx film has been successfully applied to erasable programming read-only memory (EPROM's) devices, and very good UV-erasability and reliability performances are demonstrated.

Transparent Conducting Boron-Doped Zinc Oxide Films Deposited by DC-Magnetron Sputtering in B2H6-Ar Mixtures

Transparent conducting ZnO:B films for solar cells were produced by DC magnetron sputtering in B2H6-Ar mixtures. Low-resistivity textured films could be obtained at relatively low substrate temperatures of 150-200° C. The resistivity, electron mobility and carrier concentration were 4×10-4 Ω cm, 60 cm2/ Vs and 2×1020 cm-3, respectively. The 2-µ m-thick films showed a sheet resistance of 2 Ω/ sq and optical transmission of greater than 85% at wavelengths of 0.6-1.0 µ m. These films exhibited higher optical transmission in the near infrared region than ZnO:Al films with the same resistivity because of high electron mobility. No degradation of resistivity and optical transmission was observed after exposure at 85° C and 95%RH for 5 h.

Ferroelectric and Dielectric Characteristics of (Pb1-yLay)[Mg(x+2y)/3Nb(2x+y)/3Ti1-x-y]O3 Thin Films Prepared by RF Magnetron Sputtering

Ferroelectric thin films having compositions of xPb(Mg1/3Nb2/3)O3+(1- x- y)PbTiO3+ yLa(Mg2/3Nb1/3)O3 (PLMNT) with x=0.37-0.78 and y=0.03-0.13 were prepared on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering deposition at 520° C. Pure perovskite films were obtained for all compositions. The 0.5-µ m-thick films having a constant La(Mg2/3Nb1/3)O3 content of y=0.03 showed a ferroelectric-hysteresis characteristic with the remanent polarization and coercive field decreased from 8.5 µ C/cm2 and 46 kV/cm to 4.2 µ C/cm2 and 29 kV/cm, respectively, for changing the composition from x=0.645 to 0.78. Dielectric constant (k) of 1200-1300 and dielectric loss (tan δ) less than 0.04 were also measured at 1 kHz. The temperature of dielectric peak decreased to near room temperature for an increase of Pb(Mg1/3Nb2/3)O3 content to x=0.78, which corresponded to a composition at the rhombohedral/cubic phase boundary of the PLMNT system. For films having composition lying along this phase boundary but containing La(Mg2/3Nb1/3)O3\\geqslant7 mol%, the dielectric peak became much more broadened (flattened), which provided a good dielectric stability against variation of temperature. Good dielectric stability against frequency up to 1 MHz was also observed. The films also showed weak ferroelectric-hysteresis characteristic.

Atomic structure of amorphous Al100-2xCoxCex (x=8, 9, and 10) and Al80Fe10Ce10 alloys: An XAFS study.

The local atomic structure of Co, Fe, and Ce in aluminum-rich amorphous alloys of ${\mathrm{Al}}_{100\mathrm{\ensuremath{-}}2\mathit{x}}$${\mathrm{Co}}_{\mathit{x}}$${\mathrm{Ce}}_{\mathit{x}}$ (x=8, 9, and 10) and Ce in ${\mathrm{Al}}_{80}$${\mathrm{Fe}}_{10}$${\mathrm{Ce}}_{10}$ has been investigated by x-ray-absorption fine structure (XAFS) spectroscopy. The materials, 1- and 3-\ensuremath{\mu}m-thick films, were prepared by vapor quenching using the dc magnetron sputtering method. We show that the composition of the glass-forming region of these magnetron-sputtered alloys strictly follows the theoretical limit calculated on the basis of the atomic size criterion. From analyses of the XAFS data at the K edges of Co and Fe and the ${\mathit{L}}_{3}$ edge of Ce, the following conclusions with regard to local structure are made. The first coordination sphere of Co in ${\mathrm{Al}}_{100\mathrm{\ensuremath{-}}2\mathit{x}}$${\mathrm{Co}}_{\mathit{x}}$${\mathrm{Ce}}_{\mathit{x}}$ (x=8, 9, and 10) consists of 5.8 to 6.4 Al atoms at a distance of 2.44 \AA{}. The local coordination sphere for Fe in ${\mathrm{Al}}_{80}$${\mathrm{Fe}}_{10}$${\mathrm{Ce}}_{10}$ consists of 6.4 Al atoms at a distance of 2.47 \AA{}. Ce in both systems appears to be coordinated with roughly 5 and 9 Al atoms at distances of 2.95 and 3.15 \AA{}, respectively. These results are discussed in light of the dense random packing (DRP) of hard spheres model. Both Co-Al and Fe-Al bond lengths are anomalously short (9 and 8 % contraction, respectively) with also anomalously low coordination numbers (45% reduction) from values based on the DRP model using the metallic state radii.These anomalous changes indicate a strong interaction between Co or Fe atoms and the Al atoms which perhaps may be a result of a covalently bonded environment. The Ce-Al distance in both the Al-Co-Ce and Al-Fe-Ce systems, on the other hand, is smaller by only 0.17 \AA{} (a contraction of only 5%) and the coordination number is reduced by only 13% from expected values based on the DRP model. The contraction in the distance and reduction in the coordination number for Ce are much smaller than those values of the Co or Fe and, hence, the local bonding for Ce is likely to be metallic in character.

Preparation of SrTiO3 Thin Films by Metalorganic Chemical Vapor Deposition

Strontium titanate ( SrTiO3) thin films were grown by means of the metalorganic chemical vapor deposition (MOCVD) method using dipivaloylmethane (DPM) chelate of strontium (II) [ Sr(DPM)2] and titanium tetraisopropoxide as source materials. In the preliminary experiments, the deposition behaviors of SrO and TiO2 films from respective sources were examined separately. As-grown perovskite single-phase SrTiO3 films were obtained at the substrate temperature of 750° C under the reduced pressure of 530 Pa. The films deposited on the MgO (100) substrate showed high (100) orientation and good optical transmission spectra, with the refractive index of 2.35. The dielectric constant and dielectric loss were 150–250 and 0.01–0.04, respectively. The leakage current density of the 0.38 µ m-thick films was approximately 3×10-8 A/cm2 at 3 V.

High‐Temperature Hall Measurements on Cerium Dioxide Thin Films

Simultaneous Hall and conductivity measurements have been performed on sputtered polycrystalline thin films and on bulk ceramic specimens of nearly stoichiometric CeO2 in the temperature range between 900° and 1040°C. The measurements have been performed in air using low‐frequency alternating current. In the case of the bulk ceramic specimens, an upper limit for the carrier mobility of ≤0.2 cm2/(V·s) has been obtained, which is in accordance with data from the literature for bulk samples. The conductivity of the thin films (l/1Ω·m) at 1000°C) is in accordance with data from the literature for bulk ceramics. The carrier density derived from the Hall measurements (3 × 1016/cm3 at 1000°C) increases with increasing temperature, whereas the Hall mobility (4 cm2(V·s) at 1000°C) decreases with increasing temperature. These values differ from literature data for bulk ceramic specimens. The difference may be duelo the small grain diameters (∼200 nm) in the 1‐μm‐thick thin films.

Magnetic-induction profile in a type-I superconductor by polarized-neutron reflectometry.

We have used the technique of polarized-neutron reflectometry to study the magnetic-induction profile just beneath the surface of a 1-\ensuremath{\mu}m-thick film of lead with the magnetic field applied parallel to the surface. The sample was maintained at a temperature of 1.5 K throughout the experiment, and the applied field H was varied from below ${\mathit{H}}_{\mathit{c}}$, the bulk critical field, up to the critical field for surface superconductivity, ${\mathit{H}}_{\mathit{c}3}$. From the measurements with the lead film in the bulk superconducting phase (H${\mathit{H}}_{\mathit{c}}$), we found that the spin-dependent reflectivity profiles are consistent with an exponential decay of magnetic induction with a penetration depth \ensuremath{\lambda}=39\ifmmode\pm\else\textpm\fi{}1 nm. At higher applied fields (${\mathit{H}}_{\mathit{c}}$H${\mathit{H}}_{\mathit{c}3}$) we obtained information on the diamagnetism in the surface superconducting layer. We discuss the sensitivity of the measurements to the form of the magnetic-induction profile, in particular to nonlocal effects, and show that a good description of the surface diamagnetism, over the whole range of applied fields, can be achieved with the local Ginzburg-Landau theory if the Ginzburg-Landau parameter \ensuremath{\kappa} is allowed to vary with the applied field.

Interface stability and the growth of optical quality perovskites on MgO.

An understanding of heteroepitaxy between perovskite and alkaline earth oxides is developed in terms of ion size and interfacial electrostatics. Interfacial energy minimization at the first atomic layers is the basis for a commensurate, unit-cell stability. This unit-cell stability presents the opportunity to study reduced dimensional or two-dimensional phenomena in thin-film ferroelectrics and is the basis for growth of high crystal quality, \ensuremath{\mu}m-thick films for optical device applications.

Continuous melt processing of YBCO thick films on zirconia rods

Studies of 50- mu m-thick films of YBa/sub 2/Cu/sup 3/O/sub 7- delta / on yttria-stabilized zirconia rods, which have been melt-processed using an infrared furnace, are reported. The results indicate that J/sub c/'s higher than the 3000 A/cm/sup 2/ achieved so far are not impossible. Transport and magnetization results suggest that the increase in J/sub c/ is due to alignment of the grains along the axis of the rod. This is confirmed by the scanning electron microscopy photographs, which show an increase in grain size and alignment.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>