Nanodomain and interface structure in epitaxial BaTiO<Subscript>3</Subscript> thin films on MgO deposited by magnetron sputtering

High epitaxial quality BaTiO₃ films were deposited on the MgO (001) substrate using RF magnetron sputtering at 800 °C by manipulating processing parameters. The BaTiO₃ films have a ~200 nm thickness with a very low surface roughness but a rough interface structure with respect to the substrate. The epitaxial BaTiO₃ films have a tetragonal crystal structure (a = 4.02 Å and c = 4.11 Å) with a tetragonality (c/a) of 1.02. The c-axis of the film is parallel to the growth direction as characterized by X-ray diffraction, electron diffraction, and high-resolution transmission electron microscopy. The orientation relationship between the film and the MgO is (001)_BTO//(001)_MgO and 〈100〉_BTO//〈100〉_MgO. Epitaxial nanodomains were formed in the film with a size ranging from 3 to 20 nm. The formation of the nanodomains is associated with the rough film/substrate interface due to the modification of the substrate surface characteristics (steps, terraces, and kinks) during the process. The two-dimensional interface structure between the film and the substrate was studied and its influence on the film microstructure is discussed.     

ZnO(101) films by pulsed reactive crossed-beam laser ablation

We have employed pulsed reactive crossed-beam laser ablation (PRCLA) to deposit a (101) oriented ZnO film. In this method, a supersonic jet of oxygen pulse is made to cross the laser plume from a zinc metal target while being carried to the Si(111) substrate. The obtained deposit was nanocrystalline ZnO as confirmed by a host of characterization techniques. When the substrate was held at varying temperatures, from room temperature to 900°C, the crystallinity of the obtained films increased as expected, but importantly, the crystallographic orientation of the films was varied. High substrate temperatures produced the usual (001) oriented films, while lower substrate temperatures gave rise to increasingly (101) oriented films. The substrate held at room temperature contained only the (101) orientation. The film morphology also varied with the substrate temperature, from being nanoparticulate to rod-like deposits for higher deposition temperatures. Surprisingly, the (101) orientation showed reactivity with acetone forming carbonaceous nanostructures on the surface.     

The growth and transformation of Pd2Si on (111), (110) and (100) Si

Thin Pd films on (111), (110), (100) and amorphous Si substrates form [001] fiber textured Pd₂Si in the temperature range 100°–700°C. The degree of texture is a function of substrate orientation, increasing in the order amorphous Si, (100) Si, (110) Si and (111) Si. Only on the (111) Si substrate is the Pd₂Si film epitaxially oriented. Temperature-dependent growth on this orientation can be characterized by [001] textured growth, epitaxial azimuth orientation at the Si interface and progressive layer by layer formation of the mosaic crystal to the thin film surface.During Pd deposition, rapid non-diffusion-controlled growth of epitaxial Pd₂Si on (111) Si occurs at substrate temperatures of 100° and 200°C. An unidentified palladium silicide of low crystallographic symmetry forms during Pd deposition onto a 50°C substrate. The diffusion-controlled growth of Pd₂Si on (111) Si follows a t^0.5 dependence. The velocity constant is

$\text{k = 7 × 10}{}^{\mathrm{?2}}\text{exp}\text{?}\text{29200±800}\text{RT}\text{cm}{}^2\text{/}\text{sec}$

Palladium deposited on 100°C (111) Ge substrates reacts during deposition to form epitaxially oriented Pd₂Ge. However, growth of this phase at higher temperatures results in a randomly oriented film. The transformation of Pd₂Ge to PdGe is kinetically controlled. After a 15 min anneal at 560°±10°C in N₂ only PdGe is detectable on (111) Ge.The high temperature stability of thin film Pd₂Si is controlled by time- temperature kinetics. For a given annealing cycle, the nucleation and growth rates of the PdSi phase are inversely related to the crystalline perfection of Pd₂Si. Decreasing transformation rates follow the order (100), (110), (111) Si. formation of thin film Pd₂Si occurs by the formation of PdSi and subsequent growth of Si within the PdSi phase. After a 30 min N₂ anneal, initial transformation occurs at 735°C on (100) Si, 760°C on (110) Si and 840°C on (111) Si. Extended high temperature annealing produces a two-phase structure of highly twinned and misoriented Si and small PdSi grains that penetrate as much as 3 μm into the Si.     

Influence of deposition conditions and substrate structure on the structure of sputtered tellurium films

A study has been made of the growth of tellurium films sputtered onto four substrate materials (cover glass, spinel, quartz and alumina), unheated as well as heated to 100°, 150°, 200° and 250°C. It was found that the structure of the substrate exerted no measurable influence on the structure of the films. However, sputtering conditions do influence the preferred orientation. Tellurium films sputtered onto unheated substrates have a preferred orientation of the (100) type (i.e. with the (100) planes parallel to the substrate). Those on heated substrates show a preferred orientation of the (101) type. Furthermore, thickness is an important factor. Tellurium films with thickness less than 6000 Å have a (100)-type preferred orientation, but thicker films have a (101) orientation. All the observations can be explained in terms of recrystallization taking place during deposition due to heating of the film.     

Dislocations interfaciales et cohérence dans le système épitaxique fer-or

Iron was deposited in ultrahigh vacuum onto thin single-crystal films of gold oriented with (111) parallel to the surface plane. Study by electron diffraction and electron microscopy has shown that the initial growth of iron occurs by successive monolayers. Three stages in the deposit growth have been found: first the deposited film of iron is strained to match the gold substrate exactly; then interfacial dislocations appear at the gold-iron interface; and finally iron nuclei of b.c.c. structure are formed. The interfacial dislocations are in mixed orientation with their Burgers vectors $\text{1}\text{2}$a 〈110〉 inclined to the gold-iron interface; it is found that they have a poor efficiency for accommodating the misfit between the substrate and the deposit, so that for deposits of average thickness greater than 8 Å the interface is mostly incoherent.     

Nano-cube MgO formed on silicon substrate using pulsed laser deposition

Nano-cube MgO particles were formed on Si substrates by deposition of an MgO target using pulsed laser deposition method. An epitaxial film grows on Si(001) substrate with its contraction of lattice constants. In this study, expecting high quality MgO film, the MgO film prepared in the oxygen pressure ranging from 75-400 mTorr at the high temperature of -750 degrees C. The deposited MgO showed the growth of (001) preferred orientation on the Si(001) substrate. However, X-ray Photoelectron Spectroscopy (XPS) indicated the MgO film did not form a continuous film on the Si surface. Interestingly, the surface morphology observed by an Atomic Force Microscopy (AFM) showed nano-cube MgO particles scattered on the smooth surface of Si substrate. After annealing the nano-cube MgO, the shape of MgO particles were changed from nano-cube to round shaped particles. The AFM image of the surface showed round shaped MgO nanoparticles scattered on rough surface. X-ray Diffraction (XRD) revealed the epitaxial growth of MgO(001) with cubic on cubic arrangement on the Si(001) substrate (MgO[100] parallel to Si[100]).     

Development of textures during the growth of silver films condensed in vacuum on glass

The crystal orientation of silver films evaporated onto glass in a vacuum of better than 1.33 × 10⁻³ Pa was studied as a function of the film thickness in the range 0.1–10 μm by means of the X-ray texture goniometer technique. When the substrate was at room temperature and the deposition rate was high (200 and 100 nm s⁻¹), the 111 orientation was prominent at small film thicknesses. Further film growth led to a rapid increase in the 100 orientation, which became predominant. Elevation of the substrate temperature at the same deposition rates resulted in a decrease in the number of crystallites oriented along the 100 axis, and at temperatures above 473 K the 111 orientation was dominant over the whole thickness range investigated. At a comparatively low deposition rate of 5 nm s⁻¹ at both room temperature and 573 K the crystallites were oriented with their (111) planes parallel to the substrate independent of the film thickness.     

Influence of substrate temperature and film thickness on the structure of reactively evaporated In2O3 films

Indium oxide films 25–550 Å thick were reactively evaporated at an oxygen pressure of about 0.27 Pa and at a substrate temperature between room temperature and 400°C. The dependence of the structure of the films on the substrate temperature and on the film thickness was studied using transmission electron microscopy and electron diffraction. It was found that thick films (about 550 Å) were amorphous at room temperature, partially crystallized at 50–125°C and crystalline at 150–400°C. The crystallinity of the films deposited at 150–250°C also depended markedly on the film thickness. Very thin films about 25 Å thick were quasi-amorphous, but with increasing film thickness the amorphous phase transformed into a crystalline phase.The thermal transformation of the amorphous films after deposition was also studied. Amorphous films about 550 Å thick deposited at room temperature and 100°C crystallized at 230°C and 210°C respectively.     

Textures and structures of vapor deposits

The texture of vapor deposits (PVD and CVD) changes from the orientation that places the lowest energy lattice plane parallel to the substrate under the condition of low atom or ion concentration adjacent to the deposit, to the orientation that places the higher energy crystal planes parallel to the substrate as the atom or ion concentration adjacent to the deposit increases. However, in the early stage of deposition, the deposit-substrate interface energy and the surface energy constitute the most important energies of the system. Therefore, if the lattice match is established between the substrate and the deposit without generating much strain energy, the epitaxial growth takes place to reduce the interfacial energy. When the epitaxial growth does not take place, the surface energy is dominant in the early stage of deposition and the lowest energy crystal plane tends to be placed parallel to the substrate up to a critical thickness. The critical thickness depends on the deposition conditions. If the deposition condition does not favor placing the lowest energy crystal plane parallel to the substrate, the initial texture will change to that compatible with the deposition condition as the film thickness increases, and the texture turnover thickness will be short. The microstructure and surface topography of deposits are related to their textures.     

Epitaxial growth of Ni films sputter-deposited on a GaAs(001) surface covered with a MgO film

We studied the epitaxial growth of a Ni film prepared on a GaAs(001) substrate covered with a thin epitaxial MgO buffer film, assuming that this buffer film plays a key role in the epitaxial growth of the Ni film. The MgO and Ni films were deposited by radio-frequency magnetron sputtering of the MgO and Ni targets in pure Ar gas. First, a MgO film of thickness ranging from 78 to 4.4 nm was deposited on the GaAs(001) substrate at a temperature ranging from ambient temperature to 700 °C, and then, a 136-nm-thick Ni film was deposited on the MgO/GaAs substrate at a temperature range 300-500 °C. Using transmission electron microscopy and X-ray diffractometry, we showed that the MgO film grows with the epitaxial relationship MgO(001)[001]//GaAs(001)[001] on GaAs(001) at 500 °C, and that the structure of the Ni film depends on three factors: the MgO/GaAs substrate temperature, the MgO thickness, and the annealing condition of the MgO/GaAs substrate before the Ni deposition. In conclusion, we proved that the Ni film grows with the epitaxial relationship Ni(001)[001]//MgO(001)[001]//GaAs(001)[001] on MgO/GaAs with the 4.4-nm-thick MgO film when the MgO/GaAs substrate is annealed in situ at room temperature before the Ni deposition and maintained at 300 °C during the Ni deposition.     

Epitaxial growth of Sr x Ba1−x Nb2 O6 (SBN) thin films on Pt coated MgO substrates: the determining control of platinum crystallographic orientation

The growth of (001) oriented Sr _x Ba_1−x Nb₂ O₆ (SBN:x) thin films on MgO single crystals substrates has focused attention due to its potential application to integrated signal waveguiding and electro-optic processing. This paper addresses the possible insertion of a platinum bottom electrode to implement the electro-optic effect, and examines the influence of Pt orientation on the subsequent growth of SBN thin films deposited by R.F. magnetron sputtering. We have first investigated the optimal sputtering conditions of a (001) Pt oriented growth. Experimental evidence is provided for an orientation switching temperature sensitive to R.F. power but insensitive to deposition rate which suggests that kinetic phenomena are not involved in the orientation development of Pt films. Seeding the MgO substrate with Fe, Cu or Cr inhibits the competitive (111) Pt growth without modifying the optimal temperature for (001) growth. Annealing at a temperature sufficient to crystallise the top SBN film causes a drastic evolution of the initial (111) and (001) Pt volume fractions, making particularly critical the deposition conditions for a final dominant (001) Pt texture on unseeded substrates. The (001) oriented growth of SBN is shown to occur exclusively on (001) Pt crystallites stable against subsequent annealing steps. As a final result, (001) SBN films have been obtained epitaxial on both Pt coated and not coated (001) MgO substrates. They display two in-plane orientations mirror symmetric (±α) to the axis of (001) MgO, with α shifted from 31° to 18° by (001) Pt coating.     

Structural investigation of silicon films chemically vapour deposited onto amorphous SiO2 substrates

The influence of substrate temperature and the silane-to-nitrogen ratio on the structure of silicon films 0.5–0.6 μm thick deposited onto amorphous SiO₂ substrates was investigated by X-ray diffraction. The investigations were carried out for silicon films deposited at various temperatures in the range 500–750 °C and with various silane-to-nitrogen ratios in the range 3.04 × 10^-4-2.84 × 10^-3 by volume. The silicon films deposited at 500 °C were amorphous while the films deposited at 550 °C were randomly oriented polycrystalline. The films deposited in the temperature range 600–700 °C were polycrystalline with a preferred orientation that changed from 〈110〉 through 〈100〉 to 〈111〉. The structure of the films deposited at 750 °C was randomly oriented polycrystalline. Investigations of the influence of the silane-to-nitrogen ratio on the silicon film structure revealed that the structure of films deposited at a substrate temperature of 500 °C was independent of the silane-to-nitrogen ratio. The structure of the films deposited at 600 °C depended on the silane-to-nitrogen ratio and changed from polycrystalline with a 〈110〉 preferred orientation to randomly oriented polycrystalline when the ratio was increased. The structure of films deposited at 700 °C also depended on the silane-to-nitrogen ratio and changed from randomly oriented polycrystalline to polycrystalline with double preferred orientation (〈100〉 and 〈111〉) when the ratio was increased.     

The quantitative effects of crystal habit change on the film surface form and the preferred orientation during the growth of vacuum-condensed films

Our recent systematic observations by reflection electron diffraction showed that a basic feature of film growth of high melting point materials condensed in vacuum on substrates initially at room temperature is that, after the initial thin film of randomly oriented crystals, and the growth of faces and preferred orientation of a particular type at the film surface, a new type of face and preferred orientation is often developed in further strata of deposit growth.Calculations are made showing the effect of a change in crystal habit on the film surface element distribution and the nature of the new preferred orientation which is developed.The {211} habit and orientation in gold films, in further growth after the first-developed {111} habit and orientation, is discussed as an example of the calculations, which indicate a tilt δ of approximately 25° for the {211} orientation when the vapour angle of incidence i is 45°. This agrees with our observations, confirming that the {211} orientation arises from the habit change and not from nucleation by secondary {111} twinning.     

Highly oriented (Pb, La)TiO3 thin films prepared by sol-gel process

Highly oriented lead lanthanum titanate (PLT) thin films on MgO (100) and c-plane sapphire single-crystal substrates have been prepared using the sol-gel process. The orientation and the mechanism of the highly preferred oriented PLT films derived sol-gel process have been investigated. The sol-gel PLT films fabricated on MgO (100) and c-plane sapphire substrates grow preferentially with (100) and (111) crystallographic orientations respectively, regardless of the film thickness and La content. In addition, it is confirmed that the tetragonality of the PLT perovskite structure decreases with an increase of La content. The a-axis orientation of the sol-gel PLT film on MgO (100) substrate is controlled only by formation of the intrinsic tensile stress during the crystallization of the film.     

c轴取向PbTiO3外延生长的研究

本文研究了ＭＯＣＶＤ法淀积过程中工艺条件对ＰｂＴｉＯ３膜ｃ轴取向度的影响，探讨了ＰｂＴｉＯ３膜的生长过程，通过调节氧气流量首次在ＭｇＯ（１００）单晶衬底上淀积出ｃ轴取向的ＰｂＴｉＯ３外延膜。ＰｂＴｉＯ３外延膜的介电常数为９０，折射率为２．６４，均和单晶性能一致。     

(111)-Oriented Pb(Zr0.52Ti0.48)O3 thin film on Pt(111)/Si substrate using CoFe2O4 nano-seed layer by pulsed laser deposition

Perovskite Pb(Zr_0.52Ti_0.48)O₃ (PZT) thin film with perfect (111)-orientation was achieved on CoFe₂O₄ seeded-Pt(111)/Ti/SiO₂/Si substrate by pulsed laser deposition technique using target with limited excess Pb. Pyrochlore phase formation was suppressed on Pt by CoFe₂O₄ nano-seed layer (~7 nm), and perovskite PZT was achieved at temperature as low as 550 °C. CoFe₂O₄ seed layer that has perfect (111)-orientation acts as a promoter for perfectly (111)-orientated growth of PZT. PZT film grown at 600 °C has higher degree of crystalline orientation, lower surface roughness, and compacted microstructure in comparison to the film grown at 550 °C. The PZT film has a nano-size grain-feature structure with grain size of about 40–60 nm. Perovskite formation was also confirmed by ferroelectric measurement. The ferroelectric properties of PZT film grown at 600 °C is higher than that grown at 550 °C which could be attributed to the enhancement of the crystalline orientation, crystallinity, and microstructure of the film.     

Epitaxial growth of SrRuO<Subscript>3</Subscript> thin films by RF sputtering and study of surface morphology

We report on the epitaxial growth of SrRuO₃ (SRO) thin films on Pt (111)/γ-Al₂O₃ (111) nSi (111) substrates. The grown thin films are crystalline and epitaxial as suggested by RHEED and XRD experiments. With the use of γ-Al₂O₃ (001)/nSi (001) and γ-Al₂O₃ (111)/nSi (111) substrates, crystalline but not epitaxial films have grown successfully. This result implies that lattice mismatch between nSi and SRO prevents the epitaxial growth of SRO film directly on nSi. However, the buffer Pt (111) layer mitigates lattice mismatch that provides to grow epitaxial film on nSi of quality. Morphological study shows a good surface with moderate roughness. Film grown at 700°C is smoother than the film grown at 750°C, but the variation of temperature does not affect significantly on the epitaxial nature of the films.     

Optimizing growth conditions for electroless deposition of Au films on Si(111) substrates

Electroless deposition of Au films on Si(111) substrates from fluorinated-aurate plating solutions has been carried out at varying concentrations, deposition durations as well as bath temperatures, and the resulting films were characterized by X-ray diffraction, optical profilometry, atomic force microscopy and scanning electron microscopy. Depositions carried out with dilute plating solutions (< 0.1 mM) at 28°C for 30 min produce epitaxial films exhibiting a prominent Au(111) peak in the diffraction patterns, while higher concentrations or temperatures, or longer durations yield polycrystalline films. In both epitaxial and polycrystalline growth regimes, the film thickness increases linearly with time, however, in the latter case, at a rate an order of magnitude higher. Interestingly, the surface roughness measured using atomic force microscopy shows a similar trend. On subjecting to annealing at 250°C, the roughness of the film decreases gradually. Addition of poly (vinylpyrrolidone) to the plating solution is shown to produce a X-ray amorphous film with nanoparticulates capped with the polymer as evidenced by the core-level photoelectron spectrum. Nanoindentation using AFM has shown the hardness of the films to be much higher (∼ 2.19 GPa) than the bulk value.     

Epitaxial growth of SrRuO3 thin films by RF sputtering and study of surface morphology

We report on the epitaxial growth of SrRuO₃ (SRO) thin films on Pt (111)/γ-Al₂O₃ (111) nSi (111) substrates. The grown thin films are crystalline and epitaxial as suggested by RHEED and XRD experiments. With the use of γ-Al₂O₃ (001)/nSi (001) and γ-Al₂O₃ (111)/nSi (111) substrates, crystalline but not epitaxial films have grown successfully. This result implies that lattice mismatch between nSi and SRO prevents the epitaxial growth of SRO film directly on nSi. However, the buffer Pt (111) layer mitigates lattice mismatch that provides to grow epitaxial film on nSi of quality. Morphological study shows a good surface with moderate roughness. Film grown at 700°C is smoother than the film grown at 750°C, but the variation of temperature does not affect significantly on the epitaxial nature of the films.     

Recrystallization on their substrates of Au (001)/NaCl (001) films into Au (111)/NaCl (001) Part I. Electron Microscopy and electron diffraction observations

The electron-gun evaporation technique for the deposition of Au and Ag films onto (001) NaCl leads to a decrease in the epitaxial temperatures of these materials to 75° and 50°C respectively. This decrease has enabled us to use a wide range of temperatures for film recrystallization without destruction of the substrate. The annealing of the films on their substrates leads to a change in their orientation from metal (001)/NaCl (001) to metal (111)/NaCl (001). In the present work the experimental and kinetic conditions of this transformation process are given.