The atomic structure of growth interfaces in Y–Ba–Cu–O thin films

1991 ◽  
Vol 6 (11) ◽  
pp. 2264-2271 ◽  
Author(s):  
R. Ramesh ◽  
A. Inam ◽  
D.M. Hwang ◽  
T.S. Ravi ◽  
T. Sands ◽  
...  
Keyword(s):  
Thin Films ◽  
Atomic Structure ◽  
Film Growth ◽  
Substrate Surface ◽  
Oriented Growth ◽  
Surface Steps ◽  
Nucleation Sites ◽  
Oriented Films ◽  
Second Phases ◽  
Ledge Mechanism

We have examined the atomic structure of growth interfaces in thin films of Y–Ba–Cu–O grown on [001] perovskite or cubic substrates. At substrate heater temperatures in the range of 780–820 °C c-axis oriented growth is observed on these substrates. On SrTiO3, the first layer appears to be either a BaO or a CuO2 plane while on LaAlO3 the first layer appears to be a CuO chain layer. The mismatch on the a-b plane is accommodated by the formation of interface dislocations. Defects on the substrate surface propagate as defects in the film. These defects are primarily translational boundaries and in some cases second phases. At lower substrate heater temperatures, i.e., 650–700 °C, a, b-axis growth dominates. Defects and steps on the substrate surface are more detrimental in the growth of a, b-axis oriented films, since they tend to favor the nucleation of c-axis oriented domains. This is ascribed to the ledge mechanism of c-axis film growth, for which the surface steps are good nucleation sites.

The mechanism of sputter-induced epitaxy modification in YBCO (001) films grown on MgO (001) substrates

1998 ◽  
Vol 13 (12) ◽  
pp. 3378-3388
Author(s):  
Y. Huang ◽  
B. V. Vuchic ◽  
M. Carmody ◽  
P. M. Baldo ◽  
K. L. Merkle ◽  
...  
Keyword(s):  
Buffer Layer ◽  
Film Growth ◽  
Ybco Film ◽  
Lattice Mismatch ◽  
Substrate Surface ◽  
Oriented Growth ◽  
Orientation Change ◽  
Large Lattice Mismatch ◽  
Major Factors ◽  
Hot Filament

The sputter-induced epitaxy change of in-plane orientation occurring in YBa2Cu3O7-x (001) thin films grown on MgO (001) substrates by pulsed organo-metallic beam epitaxy (POMBE) is investigated by a series of film growth and characterization experiments, including RBS and TEM. The factors influencing the orientation change are systematically studied. The experimental results suggest that the substrate surface morphology change caused by the ion sputtering and the Ar ion implantation in the substrate surface layer are not the major factors that affect the orientation change. Instead, the implantation of W ions, which come from the hot filament of the ion gun, and the initial Ba deposition layer in the YBCO film growth play the most important roles in controlling the epitaxy orientation change. Microstructure studies show that a BaxMg1-xO buffer layer is formed on top of the sputtered substrate surface due to Ba diffusion into the W implanted layer. It is believed that the formation of this buffer layer relieves the large lattice mismatch and changes the YBCO film from the 45° oriented growth to the 0° oriented growth.

Crystal Quality and Orientation of Pulsed Laser Deposited Barium Titanate Thin Films

1998 ◽  
Vol 526 ◽  
Author(s):  
J. Gottmann ◽  
T. Klotzbücher ◽  
B. Vosseler ◽  
E. W. Kreutz
Keyword(s):  
Thin Films ◽  
Kinetic Energy ◽  
Substrate Surface ◽  
Pulsed Laser ◽  
X Ray Diffraction ◽  
Oriented Growth ◽  
Axis Orientation ◽  
Film Forming ◽  
Gas Atmosphere ◽  
Krf Excimer Laser

AbstractKrF excimer laser radiation (λ=248 nm, τ=25 ns) is used for pulsed laser deposition of BaTiO3 thin films on Pt/Ti/Si multilayer substrates. The processing gas atmosphere consists of O2 at typical pressures of p=10-3-5·10-1 mbar. The investigations concentrate on the influence of the substrate temperature and the kinetic energy of the film forming particles on the crystalline structure and orientation of the growing films.X-ray diffraction measurements and polarization dependent micro Raman spectroscopy reveal oriented growth of the films with c-axis orientation normal to the substrate surface and [100] texture if the energy of the particles is > 60 eV, while at lower kinetic energies a [110] or [111] texture with partly a-axis orientation is preferred. The ferroelectricity and the dielectric constant of the films, as determined by polarization versus voltage (P-V) and capacitance versus voltage (C-V) impedance measurements, decreases with increasing kinetic energy of the film forming particles. This decrease of the dielectric properties correlates with the change of the preferred orientation and the crystalline quality of the films.

Scanning probe microscopy study of the growth of YBa2Cu3O7 thin films

1995 ◽  
Vol 53 ◽  
pp. 380-381
Author(s):  
M. Grant Norton ◽  
Rand R. Biggers ◽  
E.K. Moser ◽  
T.L. Peterson ◽  
I. Maartense
Keyword(s):  
Thin Films ◽  
Scanning Probe Microscopy ◽  
Substrate Surface ◽  
Microscopy Study ◽  
Scanning Probe ◽  
Probe Microscopy ◽  
Ybco Thin Films ◽  
Nucleation Sites ◽  
Step Flow Growth ◽  
Deposition Conditions

Previous work in our laboratory has demonstrated the use of scanning probe microscopy (SPM) techniques in the study of microstructure development in YBa2Cu3O7 (YBCO) thin films formed by pulsed-laser deposition (PLD) [e.g., Ref. 1]. Under certain deposition conditions a high density of surface outgrowths was observed. These outgrowths have been identified as a-axis-oriented YBCO grains nucleated at the substrate surface which grow in concert with the c-axis-oriented YBCO grains. This growth mechanism differs from that previously suggested for the formation of mixed a-axis-oriented/c-axis-oriented YBCO films. The microstructure of YBCO thin films deposited on vicinal substrates by PLD is very different from that observed for films grown on oriented substrates (even under equivalent deposition conditions). Films grown on vicinal LaA1O3 substrates consisted of elongated granular features oriented along common directions. The shape of these features is the result of step-flow growth where the ledges on the miscut substrates provide aligned and enhanced nucleation sites. Such features have been observed on films grown using several different deposition conditions: only the width of the features changed.

Epitaxy, microstructure, and processing-structure relationships of TiO2 thin films grown on sapphire (0001) by MOCVD

1993 ◽  
Vol 8 (10) ◽  
pp. 2634-2643 ◽  
Author(s):  
H.L.M. Chang ◽  
T.J. Zhang ◽  
H. Zhang ◽  
J. Guo ◽  
H.K. Kim ◽  
...  
Keyword(s):  
Thin Films ◽  
Single Crystal ◽  
Film Growth ◽  
Growth Parameters ◽  
Substrate Surface ◽  
Growth Conditions ◽  
Organic Chemical ◽  
Tio2 Thin Films ◽  
Growth Plane ◽  
Deposited Films

TiO2 thin films have been deposited on sapphire (0001) substrates under various conditions by metal-organic chemical vapor deposition. The structural properties of the deposited films were characterized by x-ray diffraction and transmission electron microscopy. The important growth parameters were found to be the deposition temperature and the deposition rate. The ranges studied for the two parameters were 400 to 850 °C and 10 to 120 Å/min, respectively. Depending on the growth conditions, most of the deposited films were either single-phase anatase or rutile, or a mixture of the two. These films were all epitaxial, but none of them were single-crystal films. Three distinct epitaxial relationships were observed between the films and the substrates, and, depending on the growth conditions, a deposited film can contain one, two, or all three of them. The fact that the films we obtained, although epitaxial, were never single crystal is explained based on the consideration of the difference in the rotational symmetries of the substrate surface and the film growth plane. We believe that it should be generally true that, in heteroepitaxial growth, a true single-crystal film can never be obtained as long as the point symmetry group of the substrate surface is not a subgroup of that of the film growth plane.

Magnetoresistance in Thin Films of Silver Chalcogenides

1999 ◽  
Vol 602 ◽  
Author(s):  
I.S. Chuprakov ◽  
V.B. Lyalikov ◽  
K.-H. Dahmen ◽  
P. Xiong
Keyword(s):  
Thin Films ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Vapor Transport ◽  
Oriented Growth ◽  
Linear Arrangement ◽  
Rocking Curve ◽  
Oriented Films ◽  
Geometrical Effect ◽  
Silver Chalcogenides

AbstractOriented and non-oriented thin films of silver(I) telluride, Ag2Te, were prepared by e-beam evaporation, vapor transport technique and Chemical Vapor Deposition (CVD). Crystallinity and orientation of the films were studied by Θ−2Θ XRD, rocking curve and pole figure measurements. The origin and conditions for the oriented growth are discussed. Special microdevice was prepared by photolitography from the oriented films of Ag2Te in order to investigate magnetoresistance (MR) in this material. It was proved that the reported earlier negative MR in Ag2Te films is a completely geometrical effect, which can be observed using non-linear arrangement of current and voltage contacts.

Deposition of Nanostructured Silicon Thin Films by Means of the Selective Contribution of Particles in Pecvd

1998 ◽  
Vol 507 ◽  
Author(s):  
J. Costa ◽  
P. Roura ◽  
Procai Cabarrocas ◽  
G. Viera ◽  
E. Bertran
Keyword(s):  
Thin Films ◽  
Atomic Structure ◽  
Film Growth ◽  
Direct Method ◽  
Particle Nucleation ◽  
Silicon Thin Films ◽  
Plasma Characteristics ◽  
Silicon Based ◽  
A Direct Method ◽  
Tem Grid

ABSTRACTPECVD processes are the most common way of growing amorphous and microcrystalline silicon thin films. These low pressure plasmas are known to generate large amounts of particles in the gas phase which may be a source of contamination in the production of silicon based devices. In this report, however, we show that these particles can be incorporated profitably into a growing film, provided that their size is controlled. The Modulation of the RF power is a direct method of controlling particle size. Plasma characteristics determine the dynamics of particle formation, whereas the duration of the plasma-on period controls the particle's size and atomic structure. The size and atomic structure of particles from two different periods of the same discharge were investigated. Their main characteristics, monodisperse size distribution and ordered atomic structure, are discussed in the context of the latest findings on particle nucleation and coagulation.A semi-phenomenological model was used to show that, during the first milliseconds of the discharge, particles of 1–2 nm that are electrically neutral may leave the plasma and contribute to the growth of the film. Although these particles could not be observed on the TEM grid, their contribution to film growth might be relevant.

Influence of Mn as a redox-active central metal on the electrical conduction behaviour of phthalocyanine thin films

2000 ◽  
Vol 04 (01) ◽  
pp. 23-30 ◽  
Author(s):  
D. SCHLETTWEIN ◽  
J.-P. MEYER ◽  
N. I. JAEGER
Keyword(s):  
Thin Films ◽  
Electrical Conductivity ◽  
Temperature Gradient ◽  
Charge Carrier ◽  
Seebeck Coefficient ◽  
Temperature Dependence ◽  
Thermal Activation ◽  
Film Growth ◽  
Substrate Surface ◽  
Ex Situ

Thin films of phthalocyaninatomanganese ( PcMn ) in the thickness range of 100 nm have been prepared by vapour deposition on quartz glass substrates. The films were characterized in situ during film growth and following film deposition by measurements of the electrical conductivity under DC applied electric fields parallel to the substrate surface. The dependence of the conductivity on the average film thickness was determined and the mechanism of film growth is discussed. Without breaking the vacuum, a temperature gradient was established again parallel to the substrate surface and a thermopower was detected. Its dependence on the size of the temperature gradient gave a Seebeck coefficient of –780 μV K-1 at 460 K. From the negative sign it is evident that electrons are the majority carriers in PcMn in a freshly prepared thin film. The temperature dependence of the Seebeck coefficient gave the thermal activation of charge carrier generation as ΔE = 0.19 eV , which is discussed in terms of the position of the Fermi energy in the films. The temperature dependence of the electrical conductivity gave an activation energy EA = 0.38 eV considerably higher, indicating a thermal activation of charge carrier transport and hence supporting a hopping mechanism rather than delocalized transport. Under exposure to oxygen the conductivity showed a fast small increase followed by a slow large decrease, which is discussed considering surface as well as bulk interactions. Hole conduction was measured for the completely oxidized films by a positive Seebeck coefficient. Optical spectroscopy performed ex situ was used to allow further discussion of redox interactions of the films. Evidence was found for the presence of Pc (-2) Mn (+3) O 2(-1) as well as Pc (-2) Mn (+3) O (-2) Mn (+3) Pc (-2) and Pc (-2) Mn (+2) in freshly prepared films. Films exposed to air for as long as several months were completely oxidized to Pc (-2) Mn (+3) O 2(-1).

Microstructure development of sol-gel derived epitaxial LiNbO3 thin films

1995 ◽  
Vol 10 (10) ◽  
pp. 2564-2572 ◽  
Author(s):  
Keiichi Nashimoto ◽  
Michael J. Cima ◽  
Paul C. McIntyre ◽  
Wendell E. Rhine
Keyword(s):  
Thin Films ◽  
Single Crystal ◽  
Spin Coating ◽  
Film Growth ◽  
Intermediate Phase ◽  
Substrate Surface ◽  
Sol Gel ◽  
Precursor Solution ◽  
Epitaxial Films ◽  
Epitaxial Relationship

Film growth and microstructural evolution were investigated for sol-gel derived LiNbO3 thin films deposited on lattice-matched single-crystal substrates. Epitaxial LiNbO3 films of about 100 nm nominal thickness were prepared by spin coating a solution of the lithium niobium ethoxide on sapphire (0001) substrates and annealing at 400 °C or 700 °C in a humidified oxygen atmosphere. These films exhibited an epitaxial relationship with the substrate of the type LiNbO3 (0001) || α-Al2O3 (0001) and LiNbO3 [100] || α-Al2O3 [100] as determined by x-ray pole figure analysis. Transmission electron microscopy indicated the epitaxial films annealed at 400 °C consisted of slightly misoriented ∼5 nm subgrains and of numerous ∼10 nm enclosed pores. The microstructure and orientation development of these films was consistent with a heteroepitaxial nucleation and growth mechanism, in which epitaxial nuclei form at the substrate surface and grow upward into an amorphous and porous intermediate film: Epitaxial films annealed at 700 °C contained larger 150-200 nm subgrains and pinholes. Misorientations between adjacent subgrains appeared to be significantly smaller in films annealed at 700 °C than those in films annealed at 400 °C. Hydrolysis of the alkoxide precursor solution prior to spin coating promoted the development of polycrystalline films on single-crystal sapphire substrates. Infrared spectra and thermal analysis indicated that, independent of the degree of the solution hydrolysis, nucleation of LiNbO3 was immediately preceded by decomposition of an amorphous carbonate intermediate phase.

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