High‐Speed Preparation of <111>‐ and <110>‐Oriented β‐SiC Films by Laser Chemical Vapor Deposition

Highly oriented <111> and <110> β‐SiC films were prepared on Si(100) single crystal substrates by laser chemical vapor deposition using a diode laser (wavelength = 808 nm) and HMDS (Si(CH₃)₃–Si(CH₃)₃) as a precursor. The effects of laser power (P_L), total pressure (P_tot), and deposition temperature (T_dep) on the orientation, microstructure, and deposition rate (R_dep) were investigated. The orientation of the β‐SiC films changed from <111> to random to <110> with increasing P_L and P_tot. The <111>‐, randomly, and <110>‐oriented β‐SiC films exhibited dense, cauliflower‐like, and cone‐like microstructures, respectively. Stacking faults were observed in the <111>‐ and <110>‐oriented films, and aligned parallel to the (111) plane in the <111>‐oriented film, whereas they were perpendicular to the (110) plane in the <110>‐oriented film. The highest R_dep of the <111>‐oriented β‐SiC film was 200 μm/h at P_tot = 200 Pa and T_dep = 1420 K, whereas that of the <110>‐oriented film was 3600 μm/h at P_tot = 600 Pa and T_dep = 1605 K.     

Ultra‐Fast Fabrication of <110>‐Oriented β‐SiC Wafers by Halide CVD

Φ80 mm‐diameter, highly <110>‐oriented β‐SiC wafers were ultra‐fast fabricated via halide chemical vapor deposition (CVD) using tetrachlorosilane (SiCl₄) and methane (CH₄) as precursors. The effects of deposition temperature (T_dep) and total pressure (P_tot) on the orientations, microstructures, and deposition rate (R_dep) were investigated. R_dep dramatically increased with increasing T_dep where maximum R_dep was 930 μm/h at T_dep = 1823 K and P_tot = 4 kPa, leading to a maximum of 1.9 mm in thickness in 2 h deposition. The <110>‐oriented β‐SiC was obtained at T_dep > 1773 K and P_tot = 1–4 kPa. Growth mechanism of <110>‐oriented β‐SiC has also been discussed under consideration of crystallographic planes, surface energy, and surface morphology.     

Growth of Highly (100)‐Oriented SrTiO3 Thin Films on Si(111) Substrates Without Buffer Layer

The SrTiO₃ (STO) thin films were directly grown on Si(111) substrates without buffer layer by an electron‐cyclotron‐resonance ion beam sputter deposition. The growth temperature was varied from 700°C to 850°C, while other parameters were kept unchanged. X‐ray structural analysis demonstrates that the growth temperature has a strong influence in tuning degree of (100) orientation. The STO film grown at 800°C is found to be the highest degree of (100) orientation (98%) and a strong (100) fiber texture. For the surface morphology, the development of plate‐shaped grains reveals a good correlation with the change in the degree of (100) orientation. Moreover, the leakage current–voltage characteristics of the Au/STO/Si(111) metal‐insulator‐semiconductor capacitors are investigated and discussed in considerable detail.     

High‐speed heteroepitaxial growth of 3C‐SiC (111) thick films on Si (110) by laser chemical vapor deposition

3C‐SiC (111) thick films were grown on Si (110) substrate via laser chemical vapor deposition (laser CVD) using hexamethyldisilane (HMDS) as precursor and argon (Ar) as dilution gas. The 3C‐SiC (111) polycrystalline films were prepared at deposition temperature (T_dep) of 1423‐1523 K, whereas the 3C‐SiC (111) epitaxial films were obtained at 1573‐1648 K with the thickness of 5.40 to 9.32 μm. The in‐plane relationship was 3C‐SiC [‐1‐12]//Si [001] and 3C‐SiC [‐110]//Si [‐110]. The deposition rates (R_dep) were 16.2‐28.0 μm/h, which are 2 to 100 times higher than that of 3C‐SiC (111) epi‐grown on Si (111) by conventional CVD. The growth mechanism of 3C‐SiC (111) epitaxial films has also been proposed.     

High-speed epitaxial growth of SrTiO3 films on MgO substrates by laser chemical vapor deposition

Epitaxial (100) and (111) SrTiO₃ films were prepared on (100) and (111) MgO single-crystal substrates, respectively, using laser chemical vapor deposition. The effect of deposition temperature (T_dep) on the orientation and microstructure of the SrTiO₃ films was investigated. On the (100) MgO substrates, SrTiO₃ films showed a (111) orientation at a low T_dep of 1023 K. (100) SrTiO₃ films, which were epitaxially grown at T_dep=1123–1203 K, had dense cross sections and flat surfaces with rectangular-shaped terraces. On the (111) MgO substrates, (111) SrTiO₃ films were epitaxially grown at T_dep=983–1063 K; however, these films' orientations became random at high T_dep of 1063–1113 K. The (111) SrTiO₃ films consisted of columnar grains with triangular pyramidal caps. The deposition rates of the epitaxial (100) and (111) SrTiO₃ films were 13–25 and 18–32 μm h⁻¹, respectively, which is 5–530 times higher than those obtained by MOCVD.     

High-speed deposition of silicon nitride thick films via halide laser chemical vapor deposition

Silicon nitride shows significant potential in the field of surface protection for electronic devices owing to its excellent insulation performance and mechanical properties. In this study, silicon nitride films were fabricated via halide laser chemical vapor deposition (LCVD). The effects of deposition parameters on the crystallinity, microstructure, deposition rate (R_dep), Vickers microhardness, nano-hardness and electrical resistivity were investigated. The maximum R_dep of the silicon nitride thick films was 972 µm/h at T_dep of 1573 K and P_tot of 10 kPa, which is the highest value compared with those obtained via conventional CVD. As T_dep increased, the Vickers microhardness and nano-hardness of the films increased to the highest value of 25.1 GPa and 34.8 GPa at 1573 K, respectively. The electrical resistivity of the films decreased with increasing T_dep and showed a maximum value of 1.49 × 10¹⁴ Ω·cm at T_dep of 1273 K.     

High‐Speed Preparation of Highly (100)‐Oriented CeO2 Film by Laser Chemical Vapor Deposition

CeO₂ films were prepared at deposition temperature ranged from 947 to 1096 K (corresponding laser power was from 52 to 185 W) on (100) LaAlO₃ single crystal substrate by laser chemical vapor deposition. At deposition temperature of 1027–1096 K (laser power was from 115 to 185 W), highly (100)‐oriented CeO₂ films with wedge‐caped columnar grains were prepared, whose epitaxial growth relationship was CeO₂ [100]//LAO [100] (CeO₂ [010]//LAO [011]). Their full width at half maximum of the ω‐scan on the (200) reflection and that of the ?‐scan on the (220) reflection were 0.8°–1.8° and 0.7°–1.2°, respectively. The highest deposition rate at which CeO₂ film with pure (100) preferred orientation could be obtained was 30 μm h^?1.     

Morphology and texture development of uniaxially stretched poly(ethylene naphthalene‐2,6‐dicarboxylate)

The texture development of PEN films with different semicrystalline morphologies have been studied by X‐ray diffraction. These different structures have been obtained by uniaxially stretching PEN amorphous films at 100 and 160°C (below and above T_g) at different drawing ratios. Samples have also been characterized by DSC to determine the crystallinity ratios, the crystallization, and melting temperatures. To define the orientation of crystallites in the oriented samples, pole figures have been constructed, as a function of temperature and drawing ratio (DR) in the range 1.5–4. In the range from DR = 2 to 4 the orientation is clearly uniplanar‐axial. At T_draw = 100°C the crystallinity shown by DSC analysis is higher than the sample stretched at 160°C. The orientation is also higher when samples are stretched at 100°C. The naphthalene rings mainly stay in the plane of the film with a lower fraction perpendicular to the plane of the film. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 395–401, 2007     

High-recoverable energy-storage density and dielectric tunability in Eu3+-doped NBT-xSTO binary solid solution films

The Eu³⁺-doped (1 − x)Na_0.5Bi_0.5TiO₃-xSrTiO₃ (Eu-NBT-xSTO) thin films were prepared on Pt/Ti/SiO₂/Si substrates. Raman analysis reveals that the phase structure may undergo a phase evolution of rhombohedral → rhombohedral + tetragonal (morphotropic phase boundary) → tetragonal with increasing content of STO. The scanning electron microscopy images show that the uniformity and high density of Eu-NBT-xSTO films were increased by adding STO, resulting in a pronounced effect on energy storage properties. The ɛ-T curves confirm that a high phase transition diffuseness of γ = 2.02 ± 0.03 and 1.98 ± 0.03 was achieved in Eu-NBT-0.24STO and Eu-NBT-0.3STO films, respectively. Furthermore, a large recoverable energy storage density of 31.5 J cm⁻³ with an efficiency of 64% was obtained in Eu-NBT-0.3STO film, which also exhibited good thermal stability in the temperature range between −60°C and 80°C as well as long-term stability up to 1 × 10⁸ switching cycles. These results suggest that the Eu-NBT-xSTO films may be used in the novel and advanced energy storage capacitors.     

Fast preparation of (111)‐oriented β‐SiC films without carbon formation by laser chemical vapor deposition from hexamethyldisilane without H2

(111)‐oriented β‐SiC films were prepared by laser chemical vapor deposition using a diode laser (wavelength: 808 nm) from a single liquid precursor of hexamethyldisilane (Si(CH₃)₃–Si(CH₃)₃, HMDS) without H₂. The effects of laser power (P_L), total pressure (P_tot) and deposition temperature (T_dep) on the microstructure, carbon formation and deposition rate (R_dep) were investigated. β‐SiC films with carbon formation and graphite films were prepared at P_L ≥ 170 W and P_to ≥ 1000 Pa, respectively. Carbon formation strongly inhibited the film growth. β‐SiC films without carbon formation were obtained at P_tot = 400‐800 Pa and P_L = 130‐170 W. The maximum R_dep was about 50 μm·h^?1 at P_L = 170 W, P_tot = 600 Pa and T_dep = 1510 K. The investigation of growth mechanism shows that the photolytic of laser played an important role during the depositions.     

Studies on sublimation of disperse dye out of dyed polymers. I. Rate of sublimation and amorphous transition points of poly(ethylene terephthalate)

Four samples of poly(ethylene terephthalate) film of various crystallinities and orientation were dyed with p-nitroaniline and disperse dyes. When these films were heated under a 2–3 × 10^?3 mm Hg vacuum at a specified temperature T, the dye sublimed out of the dyed specimen. The amount (M_t/M_∞) of sublimed dye is in linear proportion to the square root of the sublimation time, t^½, where M_t and M_∞ are the amounts of dye sublimed for times t and t = ∞. The diffusion coefficient D, calculated from the slope of the above plot, is independent of the dye concentration of the film. When log D is plotted against 1/T°K over the temperature range 320–520°K, the relation is composed of two to four intersecting lines with the slope decreasing with elevation of temperature and with the breaks at about 89°–98°, 122°–135°, 155° and 175°–176°C. These breaks are the amorphous transitions: the first is the glass transition temperature T_g, the second and the fourth are the amorphous transitions corresponding to the crystalline transition points, i.e., the cold crystallization temperature and the smectic–triclinic transition temperature. With some exceptions, these amorphous transitions are found also by dilatometry and electrical conductivity measurements. The apparent activation energy for diffusion decreases from about 100 kcal/mole for the glass state to 22–24 kcal/mole for the region above 180°C. The activation energy for each region changes slightly with the size of dye molecule and the crystallinity and orientation of the film.     

Preparation of highly oriented β-SiC bulks by halide laser chemical vapor deposition

Highly oriented β-SiC bulks with high hardness were fabricated by halide laser chemical vapor deposition (HLCVD) using SiCl₄, CH₄ and H₂ as precursors. The effects of total pressure (P_tot) and deposition temperature (T_dep) on the preferred orientation, microstructure, deposition rate (R_dep) and micro-hardness were investigated. The 〈110〉-oriented β-SiC bulks were obtained at low P_tot (2–4 kPa), non-oriented β-SiC bulks were obtained at mediate P_tot (6 kPa), and 〈111〉-oriented β-SiC bulks were obtained at high P_tot (10–40 kPa), exhibiting faceted, cauliflower-like and six-fold pyramid-like microstructure, respectively. The maximum R_dep of 〈111〉- and 〈110〉-oriented β-SiC bulks were 3600 and 1300 μm/h at, respectively. The activation energy obtained by the plot of lgR_dep-T_dep⁻¹ is 170 to 280 kJ mol⁻¹, showing an exponential relation with P_Si. The Vickers micro-hardness of β-SiC bulks increased with increasing P_tot and showed the highest value of 35 GPa at P_tot = 40 kPa with a complete 〈111〉 orientation.     

Roller drawing of ultrahigh molecular weight polyethylene

The roller drawing of ultrahigh molecular weight polyethylene (UHMW-PE) sheets were carried out in the roller temperature T_r range of 100–140°C. In addition to the roller drawing in the solid state (T_r = 100°C), we attempted to crystallize the molten UHMW-PE sheet under the roller-drawing process (T_r = 100–140°C). The tensile and dynamic viscoelastic properties, the molecular orientation, and the microstructure of the roller-drawn UHMW-PE sheets were investigated. The mechanical properties of UHMW-PE sheets were much improved by crystallization during the roller drawing process at T_r = 140°C. The sheets roller-drawn at T_r = 135 and 140°C exhibited c-axis orientation to the draw direction and (100) alignment in the sheet plane. However, at T_r = 100°C the elastic motion of the amorphous chains induces the twinnings of lattice, which enhances the transition to the (110) alignment in the sheet plane. The dynamic storage modulus below γ-dispersion temperature showed good correlation with crystallinity and orientation functions, while taut tie molecules and thick crystallites play an important role in the storage modulus above γ-dipersion temperature.     

Use of Self-assembled Monolayers at Variable Coverage to Control Interface Bonding in a Model Study of Interfacial Fracture: Pure Shear Loading

The relationships between fundamental interfacial interactions, energy dissipation mechanisms, and fracture stress or fracture energy in a glassy thermoset/inorganic solid joint are not well understood. This subject is addressed with a model system involving an epoxy adhesive on a polished silicon wafer containing its native oxide. The proportions of physical and chemical interactions at the interface, and the in-plane distribution, are varied using self-assembling monolayers of octadecyltrichlorosilane (ODTS). The epoxy interacts strongly with the bare silicon oxide surface, but interacts only weakly with the methylated tails of the ODTS monolayer. The fracture stress is examined as a function of ODTS coverage in the napkin-ring (nominally pure shear) loading geometry. The relationship between fracture stress and ODTS coverage is catastrophic, with a large change in fracture stress occurring over a narrow range of ODTS coverage. This transition in fracture stress does not correspond to a wetting transition of the epoxy. Rather, the transition in fracture stress corresponds to the onset of large-scale plastic deformation within the epoxy. We postulate that the transition in fracture stress occurs when the local stress that the interface can support becomes comparable to the yield stress of the epoxy. The fracture results are independent of whether the ODTS deposition occurs by island growth (T _dep = 10°C) or by homogeneous growth (T _dep = 24°C).     

Influence of the Strain on Dielectric and Ferroelectric Properties of 0.5BaZr0.2Ti0.8O3–0.5Ba0.7Ca0.3TiO3

0.5BaZr_0.2Ti_0.8O₃‐0.5Ba_0.7Ca_0.3TiO₃ ceramic and its epitaxial films on (0 0 1) SrTiO₃ substrate were prepared to compare their dielectric and ferroelectric properties. The ceramic has a high dielectric permittivity, a weak dielectric relaxation, a low ferroelectric Curie temperature (T_C) of 60°C and a fast polarization relaxation. The films show much lower dielectric permittivities and mild dielectric relaxations. Furthermore, the T_C of film with 40, 100, and 200 nm thickness is 155°C, 110°C, and 60°C, respectively, because the epitaxial strain decreases with the film thickness increasing. The higher the T_C is, the more stable the room‐temperature polarization is.     

Texture evolution of chemically deposited La2Zr2O7 buffer layer for coated conductors

A thorough study of the growth and characterization of La₂Zr₂O₇ (LZO) buffer layers prepared by chemical solution deposition on Ni–5 at% W biaxially textured substrates is presented. The main focus is to understand the processes of film growth, texture evolution, and lattice misorientation during heat treatment to obtain biaxially textured LZO buffer layers with a high degree of texture. We report a systematic investigation of LZO film growth with varying cation concentrations and processing temperatures. 45° rotated misorientation crystallization is found to coexist with the cube-on-cube orientation and maybe partially formed by the transformation of the cube-on-cube orientation with increasing annealing temperature. The texture component improves with increasing surface crystallinity. These epitaxially grown LZO buffer layers have a dense and smooth structure and a texture component of 98–99%.     

Motion mode of poly(lactic acid) chains in film during strain‐induced crystallization

How stress and temperature impact the movement of poly(lactic acid) (PLA) chains in the process of tensile film stretching was studied. The motion mode of chains was investigated through the study of the strain‐induced crystallization and orientation through changes in the draw temperature (T_d), draw ratio, and draw rate. The crystallinity and orientation degrees of the PLA films were measured by differential scanning calorimetry, Fourier transform infrared spectroscopy, and polarized optical microscopy. According to the competition between the orientation caused by the stretching and relaxation of chains under the temperature field, the motion modes of PLA chains during strain were divided into four types, modes I–IV. When T_d was 100°C, the PLA chains acted in mode I, in which the relaxation rate of chains was so fast that no crystallinity or orientation could be obtained. Beyond a draw rate of 20 mm/min at a T_d of 90°C, the type of chain movement changed from mode I to II. In mode II, only crystallites could be reserved after unloading. Chains in the PLA film moved in mode III at a T_d of 80°C; then, both the crystallization and orientation were enhanced monophonically with increasing draw rate. Beyond the draw rate of 10 mm/min at a T_d of 70°C, the orientation rate of chains was much faster than the relaxation one, and the motion mode transformed from mode III to IV. Then, obvious decreases in the crystallinity and orientation were observed with further increases in the draw rate; this resulted from the destruction of the crystallites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42969.     

Fabrication and electrical properties of SrTiO3/diamond junctions

Strontium titanate (STO) films were directly deposited on Ib (100) single crystal diamond by r.f. magnetron sputtering. The as-deposited STO film was in amorphous state. On the other hand, the crystalline STO film was obtained under the optimized condition of a deposition temperature of 250 °C and a post-annealing temperature of 650 °C. STO/diamond junctions were fabricated on boron-doped homoepitaxial layers grown on p⁺-type single crystal diamond substrates. Electrical properties of the STO/diamond junction were investigated by changing the surface terminations of diamond with hydrogen or oxygen and the crystallinity of the STO film. It was found that the amorphous STO acted like a semi-insulator on H-diamond surface and that the amorphous STO/O-diamond junction behaved like a Schottky diode. The crystalline STO/O-diamond showed a complex rectifying behavior. The crystalline STO film possessed a higher dielectric constant as compared to that of the amorphous one.     

Effect of deposition temperature on the growth of Y1Ba2Cu3O7−x thin film by aerosol assisted chemical vapor deposition using liquid solution sources

We have investigated the effect of the deposition temperature on the growth of Y₁Ba₂Cu₃O_7−x (YBCO) thin film using liquid solution sources on MgO (100) single crystalline substrate and have characterized the superconducting properties. The YBCO films were prepared by aerosol assisted chemical vapor deposition (AACVD). Single solution source of Y, Ba, and Cu β-diketonates dissolved in tetrahydrofuran (THF) was used as precursor. This precursor was passed through an ultrasonic aerosol generator and transported into a hot-wall CVD reactor using Ar as reactant gas (400 secm). The substrate was placed normal to the gas stream and the substrate temperature was varied from 760 to 860 °C. Deposition was carried out in oxygen atmosphere maintaining total pressure of 3.2 Torr inside the chamber. Deposition time was also varied from 10 to 30 min. The grown YBCO thin films were highly oriented to (001) orientation perpendicular to the substrate. The film deposited at 815 °C had a sharp transition to superconducting state about 87 K. The activation energy estimated from the Arrhenius plot is ∼19.14 kJ/mol at the deposition temperature of 815 °C.     

Optimized Growth of Heteroepitaxial (111) NiFe2O4 Thin Films on (0001) Sapphire with Two In‐Plane Variants via Chemical Solution Deposition

(111)‐oriented epitaxial thin films of nickel ferrite (NFO) are grown on c‐plane sapphire [α‐Al₂O₃(0001)] substrates using a chemical solution deposition technique. The processing conditions, including pyrolysis and annealing temperatures, are varied to achieve a film that shows maximum texture and epitaxy. It is shown that increasing the pyrolysis temperature to 400°C and decreasing the annealing temperature to 750°C for 10 min result in the highest degree of texture in the films. Lower film thickness also leads to a higher degree of texture. Microstructural studies confirm an in‐plane epitaxial relationship between the (111) NFO film and the (0001) Al₂O₃ substrate in two variants, [110]_NFO || or .