Laser Chemical Vapor Deposition Research Articles

Highly (100)-oriented Ce 1 − xFe xO 2 − δ solid solution films prepared by laser chemical vapor deposition

Ce 1 − x Fe x O 2 − δ solid solution films were prepared on amorphous silica substrates by laser chemical vapor deposition using metal dipivaloylmethanate precursors and a semiconductor InGaAlAs (808 nm in wavelength) laser. X-ray diffraction revealed the formation of single Ce 1 − x Fe x O 2 − δ phase at x ≤ 0.15, while CeO 2 and Fe 2O 3 phases were found for higher Fe content. Highly (100)-oriented Ce 1 − x Fe x O 2 − δ ( x = 0.02) films were obtained at laser power, P L = 50–200 W and deposition temperature, T dep = 800–1063 K. Lotgering factor (200) was calculated to be above 0.8 for films prepared at P L = 50–150 W. X-ray photoelectron spectroscopy revealed the presence of Fe 3+, Ce 4+ and Ce 3+ on solid solution films. Cross-sectional transmission electron microscope images disclosed a film columnar feather-like structure with a large number of nano-scale interspaces. Deposition rates were 2 or 3 orders of magnitude higher than those reported for conventional metal organic chemical vapor deposition of CeO 2.

High-speed preparation and dielectric properties of BaTi4O9 film by laser chemical vapor deposition

BaTi4O9 film was prepared on Pt/Ti/SiO2/Si substrate by laser chemical vapor deposition. The microstructure and dielectric properties were investigated. The single-phase BaTi4O9 film with random orientation was obtained. The surface consisted of round and rectangular grains, and the cross-section was columnar microstructure. The deposition rate (R dep) was 135 μm h−1. The dielectric constant (e r) and loss (tanδ) were 35 and 0.01, respectively, at 1 MHz. With increasing temperature, e r increased and showed a broad peak around 736 K, which indicated there might be a phase transition.

Transparent interconnections formed by rapid single-step fabrication of graphene patterns

We developed a process to form transparent interconnections using graphene patterns that were synthesized by laser chemical vapor deposition. The number of graphene layers was tightly controlled by laser scan speed. Graphene patterns were fabricated at a high scan speed of up to 200 μm/s with a single-step process. The process time is about a million times faster than the conventional chemical vapor deposition method. The fabricated graphene patterns on nickel foils were directly transferred to desired positions on patterned electrodes. The position-controlled transfer with rapid single-step fabrication of graphene patterns provides an innovative pathway for graphene-based interconnections.

Temperature-dependent photoconductance of heavily doped ZnO nanowires

Ga-doped ZnO nanowires have been synthesized by a pulsed laser chemical vapor deposition method. The crystal structure and photoluminescence spectra indicate that the dopant atoms are well integrated into the ZnO wurtzite lattice. The photocurrent properties at different temperatures have been systematically investigated for nanowires configured as a three-terminal device. Among the experimental highlights, a pronounced semiconductor-to-metal transition occurs upon UV band-to-band excitation. This is a consequence of the reduction in electron mobility arising from the drastically enhanced Coulomb interactions and surface scattering. Another feature is the reproducible presence of two resistance valleys at 220 and 320 K upon light irradiation. This phenomenon originates from the trapping and detrapping processes in the impurity band arising from the native defects as well as the extrinsic Ga dopants. This work demonstrates that due to the dimensional confinement in quasi-one-dimensional structures, enhanced Coulomb interaction, surface scattering, and impurity states can significantly influence charge transport. Open image in new window

Ternary Phase Relation on Preparation of YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-δ</sub> Films by Laser CVD

c-axis-oriented YBa2Cu3O7- films were prepared by laser chemical vapor deposition (laser CVD) using Y(DPM)3, Ba(DPM)2/Ba(TMOD)2 and Cu(DPM)2 as precursors with enhancement by a continuous wave Nd:YAG laser. YBa2Cu3O7- film almost in a single phase and that with different second phases of BaCuO2, CuBaO2, BaY2O4, CuYO2, Y2O3 and CuO were obtained by varying evaporation temperature of precursors. Ternary phase diagram as a function of evaporation amount of three precursors were obtained. The deposition rate of the c-axis-oriented YBCO film was 60 µmh-1, about 60–600 times higher than those of conventional CVD.

Effect of NH3 Atmosphere on Preparation of Al2O3-AlN Composite Film by Laser CVD

Al2O3-AlN composite film was first prepared by laser chemical vapor deposition (laser CVD) using aluminum acetylacetonate (Al(acac)3) and ammonia (NH3) as source materials. The effects of NH3 on the crystal phase, composition and microstructure were investigated. The crystal phase changed from α-Al2O3 to AlN gradually with increasing the mole ratio of NH3 to Ar. Al2O3-AlN composite film was obtained at NH3/Ar ratio ranged from 0.09 to 0.16 (Tdep = 862–887 K), and AlN granular grains were embedded in between α-Al2O3 polyhedral grains.

ChemInform Abstract: Catalytic Materials Prepared by Chemical Vapor Deposition

AbstractReview: 44 refs.

Synthesis of nanometric iron oxide films by RPLD and LCVD for thermo–photo sensors

Iron oxide films were deposited on Si substrates by reactive pulsed laser deposition (RPLD) using a KrF laser (248 nm). These films were deposited too by laser (light) chemical vapor deposition (LCVD) using continuous ultraviolet photodiode radiation (360 nm). The deposited films demonstrated semiconducting properties. These films had large thermo-electromotive force (e.m.f.) coefficient (S) and high photosensitivity (F). For films deposited by RPLD the S coefficient varied in the range 0.8–1.65 mV/K at 205–322 K. This coefficient depended on the band gap (E g ) of the semiconductor films, which varied in the range 0.43–0.93 eV. The largest F value found was 44 Vc/W for white light at power density I≅0.006 W/cm2. Using LCVD, iron oxide films were deposited from iron carbonyl vapor. For these films, the S coefficient varied in the range −0.5 to 1.5 mV/K at 110–330 K. The S coefficient depended on E g of the semiconductor films, which varied in the range 0.44–0.51 eV. The largest F value of these films was about 40 Vc/W at the same I≅0.006 W/cm2. Our results showed that RPLD and LCVD can be used to synthesize iron oxide thin films with variable stoichiometry and, consequently, with different values of E g . These films have large S coefficient and high photosensitivity F and therefore can be used as multi-parameter sensors: thermo–photo sensors.

(006)-oriented α-Al2O3 films prepared in CO2–H2 atmosphere by laser chemical vapor deposition using a diode laser

Abstract (0 0 6)-oriented α-Al2O3 films were prepared by laser chemical vapor deposition (LCVD) using aluminum acetylacetonate (Al(acac)3) in CO2–H2 atmosphere. The effects of the CO2 mole fraction ( F CO 2 ) and laser power (PL) on the crystal phase, microstructure, and deposition rate (Rdep) were investigated. α- and γ-Al2O3 mixture films were prepared at PL = 90 W (deposition temperature of 818 K), whereas (0 0 6)-oriented single-phase α-Al2O3 films were obtained at PL = 110 W (863 K). The texture coefficient and the grain size of the (0 0 6)-oriented films increased with increasing F CO 2 . The orientation of the α-Al2O3 films changed from (0 0 6) to (1 0 4) to (0 1 2) with increasing PL (Tdep). The Rdep of the (0 0 6)-oriented α-Al2O3 films increased with increasing F CO 2 .

One step production of magnetic nanoparticle films by laser pyrolysis inside a chemical vapour deposition reactor

Deposition of nanoparticulated films onto glass has been achieved by using an unprecedented combination of laser pyrolysis and chemical vapour deposition (CVD) on a single step process. Characterisation of the films reveals that the coated glasses obtained by this technique have similar characteristics to the ones previously fabricated using a two step pyrolysis plus CVD process. Under the laser action, maghemite or hematite nanoparticulated coatings are obtained by varying the processing conditions. We envisage the incorporation of this one step process for industrial production, where the nanoparticulated film would be deposited as the glass moves along the production line.

High-speed epitaxial growth of (100)-oriented CeO 2 film on r-cut sapphire by laser chemical vapor deposition

(100)-oriented CeO 2 film was prepared on r-cut sapphire ( ( 1 1 ¯ 02 ) Al 2O 3) by laser chemical vapor deposition at laser powers from 123 to 182 W with deposition temperatures ranging from 1042 to 1122 K. The (100) CeO 2 films grew epitaxially on ( 1 1 ¯ 02 ) Al 2O 3 substrate with the in-plane orientation relationship of CeO 2 [010] // Al 2O 3 [ 1 ¯ 101 ] and CeO 2 [001] // Al 2O 3 [ 11 2 ¯ 0 ] . The surface morphology of the CeO 2 films was characterized by elongated grains with truncated pyramidal cap. The deposition rate of the CeO 2 film was 10–15 μm h − 1 , about 10–15 times higher than those of conventional metalorganic CVD.

Catalytic materials prepared by chemical vapor deposition

In the 1980's appeared the first several scientific papers dealing with chemical vapor deposition (CVD) of nanostructured catalytic materials. Since then, the tremendous increase in the number of related publications indicates the significant importance of CVD for the preparation of catalysts. CVD has the capability to generate various types of catalytically attractive nano-scale structures by modifying the surface properties of massive or even nano-divided substrates. Relatively new CVD processes such as catalytic CVD, fluidized-bed CVD, rotary CVD, two-step CVD and large spot laser CVD allow the formation of nanoparticles, nanotubes, nanofibers, nanocomposites and porous or oriented films. Intensive research is being performed on the production of CNTs and the preparation of supported catalysts by CVD. This paper provides an overview of the relatively new CVD processes involved in the preparation of catalytic materials and some representative examples reported in the open literature.

Cr2O3 thin films grown at room temperature by low pressure laser chemical vapour deposition

Chromia (Cr2O3) has been extensively explored for the purpose of developing widespread industrial applications, owing to the convergence of a variety of mechanical, physical and chemical properties in one single oxide material. Various methods have been used for large area synthesis of Cr2O3 films. However, for selective area growth and growth on thermally sensitive materials, laser-assisted chemical vapour deposition (LCVD) can be applied advantageously.Here we report on the growth of single layers of pure Cr2O3 onto sapphire substrates at room temperature by low pressure photolytic LCVD, using UV laser radiation and Cr(CO)6 as chromium precursor. The feasibility of the LCVD technique to access selective area deposition of chromia thin films is demonstrated. Best results were obtained for a laser fluence of 120mJcm−2 and a partial pressure ratio of O2 to Cr(CO)6 of 1.0. Samples grown with these experimental parameters are polycrystalline and their microstructure is characterised by a high density of particles whose size follows a lognormal distribution. Deposition rates of 0.1nms−1 and mean particle sizes of 1.85μm were measured for these films.

Deposition of .ALPHA.-Al2O3 films on Ti(C, N)-based cermet substrate by laser chemical vapor deposition using a diode laser

α-Al2O3 film was first deposited on Ti(C, N)-based cermet substrate by laser chemical vapor deposition (LCVD) in a CO2–H2 atmosphere. The effects of atmosphere, laser power (PL), total pressure (Ptot) and deposition temperature (Tdep) on the crystal phase and microstructure were investigated. α- and γ-phase mixture film was prepared at Tdep = 833 K. Single phase α-Al2O3 film was obtained at Tdep = 903 K. The surface morphology of α-Al2O3 film changed from a cauliflower-like to a granular-like structure with increasing Tdep and decreasing Ptot. α-Al2O3 film with a well-developed facet structure was obtained at Ptot = 0.6 kPa and Tdep = 933 K.

(100)-oriented CeO2 films prepared on (100) SrTiO3 substrates by laser chemical vapor deposition

(100)-oriented CeO2 films prepared on (100) SrTiO3 substrates by laser chemical vapor deposition

Laser chemical vapor deposition of TiN film on Ti(C,N)-based cermet substrate using Ti(OiPr)2(dpm)2-NH3 system

TiN films were prepared on Ti(C,N)-based cermet substrate by laser chemical vapor deposition using titanium isopropoxide dipivaloylmethane [Ti(OiPr)2(dpm)2] and ammonia (NH3) as precursors. The effects of deposition temperature (Tdep) and laser power (PL) on the crystal phase, microstructure and adhesion were investigated. TiN film was prepared at Tdep > 903 K (PL > 100 W). The microstructure of TiN film changed from rose-like grains to pyramid-like grains to aggregate grains with increasing PL and Tdep. Highly adhesive film was obtained at moderate Tdep = 1047 K (PL = 120 W).

CVD Grown Materials for High Temperature Electronic Devices : A Review

Chemical Vapour Deposition (CVD) remains an extremely popular area of fabricating electronic devices, operating at high temperature and in harsh environments. CVD offers an excellent process controllability and development of quality thin films on varieties of substrates that are compatible to standard IC technology. Plasma enhanced CVD (PECVD), atomic layer CVD (ALCVD), laser CVD and metal organic CVD (MOCVD) need special mention for their added advantages like low substrate temperature, high spatial resolution and precise doping, in addition to the high temperature stability of the films. In this review article, we critically discuss the various standard CVD processes for electronics industry and some high temperature non-oxide ceramic materials like SiC, III-nitrides and carbon nanotubes for electronic device applications. These include optoelectronics devices like laser diode, laser crystal cooling, microwave device, power semiconductor heat spreaders and high temperature pressure and chemical sensors. The prospect of the most recently reported CVD grown graphene for high temperature device applications has been highlighted.

Preparation of BaTi2O5 films on (100), (110) and (111) MgO substrates by laser CVD

Preparation of BaTi2O5 films on (100), (110) and (111) MgO substrates by laser CVD

Fast epitaxial growth of a-axis- and c-axis-oriented YBa2Cu3O7−δ films on (1 0 0) LaAlO3 substrate by laser chemical vapor deposition

a-axis- and c-axis-oriented YBa2Cu3O7−δ (YBCO) films were epitaxially grown on (100) LaAlO3 substrates by laser chemical vapor deposition. The preferred orientation in the YBCO film changed from the a-axis to the c-axis with increasing laser powers from 77 to 158W (the deposition temperatures from 951 to 1087K). The a-axis-oriented YBCO film showed in-plane epitaxial growth of YBCO [001]//LAO [001], and the c-axis-oriented YBCO film showed that of YBCO [010]//LAO [001]. A c-axis-oriented YBCO film with a high critical temperature of 90K was prepared at a deposition rate of 90μmh−1, about 2–1000 times higher than that of metalorganic chemical vapor deposition.

High-speed growth of YBa2Cu3O7 − δ film with high critical temperature on MgO single crystal substrate by laser chemical vapordeposition

a-axis- andc-axis-orientedYBa2Cu3O7 − δ films were prepared on a (100) MgO single crystal substrate by chemicalvapor deposition enhanced by a continuous wave Nd:YAG laser. Ac-axis-oriented YBCO film with a critical temperature of 89 K was prepared at a high deposition rateof 57 µm h − 1, about 2–600 times higher than that of conventional chemical vapor deposition.