Oxides formed on the (111) surface of lead II. Red PbO or litharge

The electron microscopy of oxidized lead films revealed that the oxide consists of a yellow PbO layer in which small (10^?17?10^?18 cm³) rectangular islands of red PbO are dispersed. The red PbO islands are thicker than the yellow PbO layer and are oriented with their $\text{[0}\text{2}\text{1]}$ direction approximately perpendicular to the (111) surface of the lead film. Moiré fringe patterns visible in the red PbO islands show that their lattices are bent. The magnitude and sign of this bendings was measured. It was found that the bending enables the red PbO islands to satisfy one epitaxial orientation near their center and two forms of another near their ends. However, the bending does not arise entirely from an attempt to satisfy two epitaxial relationships simultaneously. The bending seems to result promaroly from a gradient in the oxygen concentration. As this gradient is unlikely to be constant it is probable that a true elastic strain is also present. Simple explanations for the sign of the lattice bending and for the shape and orientation of the red PbO grains are proposed.     

Crystallography of epitaxially grown molybdenum on sapphire

Molybdenum thin films were deposited onto (0001), ($\text{1012}$) and (10$\text{12}$) sapphire substrates by electron-beam evaporation in ultrahigh vacuum. The surface morphology and crystallographic orientation of these films were characterized by electron microscope replication and reflection electron diffraction. The effect of the crystallographic plane of the sapphire substrates as well as that of the deposition rate on the crystallographic orientation of the deposited molybdenum films were examined in the temperature range 25°-1000°C. The epitaxial temperature range was 600°-900°C for basal plane substrates and 300°-1000°C for ($\text{1}$012) and (10$\text{1}$2) substrates. The orientation of the deposited film was strongly dependent on that of the sapphire substrate.     

Epitaxial lead chalcogenide films: Orientation on substrates with the fluoride structure

Epitaxial films of the lead chalcogenides on (111)-oriented CaF₂, SrF₂ and BaF₂ substrates are azimuthally rotated by $\text{(2n ? 1)π}\text{3}$ relative to the substrate, e.g. (111)∥(111) but [10$\text{1}$]∥[$\text{1}$01]. It is shown that a model based on nearest and next-nearest neighbor interactions between the film and its substrate (over a sequence of five atomic (111) layers) leads to an interface structure that accounts for the experimentally observed orientation.     

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.     

Heteroepitaxy of Ir films on silicon with a ceria/yttria stabilized zirconia buffer layer

Heteroepitaxial Ir films on Si(001) with a double ceria/yttria stabilized zirconia heteroepitaxial buffer layer were grown by magnetron sputtering. As-deposited CeO₂ films covered with {111} faceted pyramids resulted in iridium films with the [001] axis normal to the substrate plane. The buffered substrates annealed at 1115 °C have a smooth surface; Ir films on such substrates have the (111) orientation and consist of grains turned at 90° toward each other.     

The structure of nickel and cobalt films on the (111) surface of n-type silicon

Films of Ni and Co have been grown on the (111) surface of phosphorus doped n-type silicon by evaporation in high vacuum. For both systems polycrystalline films resulted for all substrate temperatures except in the range 250° to approximately 400°C when f.c.c. Ni or Co grew with the orientation Ni/Co (110)6Si (111); Ni/Co [$\text{1}$10]6Si [$\text{2}$11].     

Some observations on the fracture of electrodeposited single-crystal nickel films

Single-crystal films of nickel with (110), (111) and (211) as the film plane were fractured with the applied stress in different directions; the resulting fracture edges were examined using electron microscopy. The type of fracture depended upon the plane and orientation, varying from twin-free cleavage on (110) with the applied stress along the [001] to lattice distortion with no twins and disintegration of the sample on (110) with the applied stress along [1$\text{1}$0]. In the intermediate cases where twins were associated with the fracture, evidence of extrinsic faults was observed but no unambiguous evidence of intrinsic twins.     

Growth of monocrystalline CdS films on mica surfaces through amorphous interfacial layers of silicon monoxide and carbon by chemical transport reactions

The oriented crystallization of CdS through amorphous interfacial layers of silicon monoxide and carbon by the method of chemical transport reactions has been studied. Cleaved mica (muscovite) single crystals were used as substrates. The interfacial layer thicknesses ranged from 70 to 150 Å. The informative ability of the interfacial layers was checked using the method of decoration with anthraquinone. Epitaxial CdS films 3–15 μm thick were obtained on top of the amorphous interfacial layers, with the (0001) CdS plane parallel to the (001) cleavage plane of mica and the direction [10$\text{1}$0]_CdS coinciding with [110]_mica, which corresponds to the orientation of CdS films prepared directly on the mica surface. The structural perfection of CdS films obtained through interfacial silicon monoxide and carbon layers was practically the same as that of films grown on the mica surface with no interfacial layers. For interfacial layer thicknesses exceeding 120 Å for SiO and 100 Å for carbon, the informative properties of the layers vanished and the CdS films were polycrystalline. The suggestion is made that chemical transport reactions leading to oriented crystallization can proceed without direct contact of the reacting components with the surface of the single-crystal substrates.     

Epitaxial growth on MgO on (001) surfaces of silver single-crystal film substrates

The epitaxial growth of evaporated MgO films (<25–4000 Å) on smooth (001) surfaces of silver single-crystal film substrates at a temperature inthe range 25°–200°C has been studied by reflection high energy electron diffraction. At substrate temperatures below 150°C, MgO is oriented with its (111) plane parallel to the surface of the substrate. The (111) orientation is fibrous. At 150°C a major fraction of the deposit is oriented in parallel and at 200°C only the parallel orientation is observed. The deposit initially grows as oriented three-dimensional nuclei. As the film thickness increases to 500 Å, randomly oriented MgO is simultaneously formed at the surface. With further increase in thickness the degree of epitaxial orientation decreases and at 1000 Å a small amount of one- degree (111) orientation appears at the surface. At 4000 Å the surface orientation becomes one-degree (111); the (111) orientation is interpreted as a final growth orientation.     

Interdiffusion phenomena in Au/Cu and Cu/Au bilayers

The microstructures of epitaxial deposits of (111) Cu/(111) Au and (111) Au/(111) Cu at various stages of interdiffusion are described. The most prominent microstructural features of Au/Cu films (where gold deposition occurred at temperatures less than 400 °C) were (Matthews) coincidence lattice misfit dislocations lying along < 1$\text{1}$0 > directions in the film plane with $\text{|b| =}\text{a}\text{2}\text{< 110 >}$ directed out of the film plane. Their spacings, transmission electron microscopy (TEM) hot stage behavior and generation mechanisms are discussed. For more severe diffusion anneals, the coincidence dislocation density decreased and hexagonal networks identified as ( van der Merwe) natural lattice misfit dislocations became resolvable. They are edge type (lying along <11$\text{2}$> directions in the film plane) with $\text{|b| =}\text{a}\text{2}\text{< 1}\text{1}\text{0 >}$. For the case of Cu/(111) Au bilayers, copper deposited at and below 315 °C with a 20 min anneal again showed coincidence misfit networks. Higher temperature deposition of copper (or hot stage annealing) resulted in natural lattice misfit dislocations in the microstructure. The densities of both types of dislocations were determined and their TEM hot stage behavior was investigated. The method by which the two networks contribute to the relief of misfit strain in both bilayers is discussed.     

Roles of lattice fitting in epitaxy

The epitaxial orientations of three series of materials-alkali halides, chalcogenide compounds and face-centered cubic metals-and of indium (face-centred tetragonal structure) and iron (body-centred cubic structure) on a (001) MgO substrate were examined by in situ electron microscopy and diffraction. The lattice parameter ratio ? = a_d/a_s (d, deposit;s, substrate) ranges from 0.95 for LiF to 1.68 for KI, from 1.41 for PbS to 1.53 for PbTe and from 0.84 for nickel to 1.18 for lead. A systematic dependence of the epitaxial orientation on ? is found: alkali halides and chalcogenide compounds with ? around 1 or 1.5 prefer the (001) parallel orientation with (001)_d(001)_s, [100]_d[100]_s, but those with a value of ? around √2 prefer the (001) orientation with (001)_d(001)_s, [110]_d[100]_s. Metals with ? near 1 also prefer the (001) parallel orientation, but copper and nickel with ? around 0.85 prefer the (1$\text{1}$0) orientation with (1$\text{1}$0)_d(001)_s, [11$\text{2}$]_d[100]_s, and gold, indium and lead with values of ? of 0.97, 1.17 (1.09) and 1.18, respectively, favour the (111) orientation with (111)_d(001)_s, [1$\text{1}$0]_d[1$\text{1}$0]_s. The epitaxial relation is discussed in terms of the fit of the lattice spacings of the deposit and substrate crystals.     

Characterization of dislocations in copper electrodeposits

Copper electrodeposits with the [111] orientation were obtained from a copper sulfate bath consisting of 280 g/l CuSO₄5H₂O and 80 g/l H₂SO₄ at 30°C. The cathode current density was 900 to 1300 A/m². Dislocations in the electrodeposits were characterized using transmission electron microscopy. Dislocations in each of the (111) grains could be classified into two groups. One group belonged to high density dislocation bundles radiating from one small area, and another group was located between the bundles. The dislocations in the first group were directed along the <112< directions parallel to the (111) plane and of the edge type. About 42 pct of the dislocations in the second group were also parallel to the (111) plane and of the mixed type. In summary, the majority of dislocations in the (111) grains was of edge type lying on the (111) plane.     

Reflection high energy electron diffraction and X-ray studies of AlN films grown on Si(111) and Si(001) by organometallic chemical vapour deposition

The crystallinity of AlN films on silicon substrates grown by organometallic chemical vapour deposition was investigated using X-ray diffraction and reflection high energy electron diffraction (RHEED). Single-crystal films of good quality with atomically smooth surfaces can be epitaxially grown on Si(111) substrates. Epitaxial films can also be grown on Si(001) substrates. These films have previously been reported to have a fibre structure. Different RHEED patterns were observed from the films on Si(111) and Si(001). It is established that the films grown on Si(001) consist of two types of crystallite with the following orientations: [11$\text{2}$0]_AlN//[110]_Si and [11$\text{2}$0]_AlN//[1$\text{1}$0]_Si The thickness dependence of the crystallinity was also investigated. The standard deviation σ of the X-ray rocking curve for the films grown on Si(111) is less than that for the films on Si(001) and is independent of the film thickness. The σ values for the films on Si(001) decrease markedly with increasing film thickness. On the basis of these observations, the growth mechanism of AlN epitaxial films on Si(111) and Si(001) is discussed.     

Preparation of hexagonal potassium tungsten bronze thin films by thermal vacuum evaporation

$\text{K}{}_{\mathrm{x}}\text{WO}{}_{\mathrm{<mtext>3+</mtext><mtext>x</mtext><mtext>2</mtext>}}\text{(}\text{x}\text{= 0.3)}$ thin films have been prepared by the thermal vacuum evaporation technique. Depending on the substrate temperature during deposition, either amorphous or crystalline films could be obtained. X-ray diffraction patterns and pole-figure information revealed that fresh crystalline films deposited on a hot (about 400°C) substrate of indium-tin oxide on glass microscope slides had a preferred orientation, with the c-axis perpendicular to the surface of the film. SIMS depth profiles and RBS experiments were used to confirm the stoichiometry and uniformity of the chemical components in the thermally deposited films.     

Crystal orientation changes of Ag thin films on the Si(111) substrate due to tribo-assisted recrystallization

Crystal orientation changes of Ag thin films due to the tribo-assisted recrystallization have been studied using grazing incidence X-ray diffraction with synchrotron radiation. After preparation of an Si(111) √3 × √3-Ag surface, a 5-nm-thick Ag film was deposited on the surface at the substrate temperature of 303 K in an ultra-high vacuum chamber. The friction experiments were carried out using a diamond pin-on-plate type tribometer just after the Ag deposition in the same UHV chamber. We found that the coefficient of friction of the Ag films on the Si(111) √3 × √3-Ag surface decreases from 0.07 to 0.03, with increasing reciprocal sliding cycles. In synchronization with the coefficient change, Ag{100} grains are gradually disappearing. As a result, the Ag{111} grains cover the entire surface after 50 sliding cycles. Moreover, we found that the domain size of the Ag{111} grains increases with increasing reciprocal sliding cycles by measuring the rocking curve width. These results directly show that the Ag(111) plane is the sliding plane of friction and the coefficient of friction of Ag films is determined by the fraction of the Ag(111) grains in the Ag films. Moreover, to clarify the reaction between the Ag film and the Si substrate due to the tribo-assisted recrystallization, the substrate strain has been studied by an extremely asymmetric X-ray diffraction technique using synchrotron radiation.     

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.     

Far-infrared reflection spectra of AgInSe2 and AgInTe2

The reflectivity of polarized light was measured, with a Michelson interferometer in the range between 10cm^?1 and 400cm^?1, on an artificial plane surface cut from oriented single crystal of AgInSe₂ with $\text{E}\text{?}\text{∥}\text{c}\text{?}$ and $\text{E}\text{?}\text{⊥}\text{c}\text{?}$, and on a natural (112) surface of AgInTe₂ with $\text{E}\text{?}\text{∥{111}}$ and $\text{E}\text{?}\text{⊥{111}}$. The results were analyzed by the Kramers-Kroning method and the least-squares fitting of the classical dispersion formula. The main features of the spectra and the form of the polarization vectors of some modes are discussed.     

Epitaxy of copper on muscovite mica

The vapour deposition of copper onto air-cleaved mica (001) has been studied by reflection high energy electron diffraction in ultrahigh vacuum. At room temperature, crystallites with random orientation and crystallites with Cu(111)mica (001) and Cu[1$\text{1}$0]mica [100] (orientation I) or Cu[1$\text{1}$0]mica [010] (orientation II) are observed. On annealing, either orientation I or orientation II dominates. Also at room temperature, good epitaxy of copper on Cu(111) occurs. Deposition at 570 K always leads to a single-crystal film in orientation I. During early growth, however, crystallites in both orientations appears to have comparable importance, but those with orientation I grow at the expense of those with orientation II during coalescence.     

Three-dimensional elastic-plastic finite element analysis of small surface cracks

Three-dimensional, elastic and elastic-plastic finite element analysis of small surface cracks was performed. The elastic analysis is in good agreement with other solutions. For a round surface with a radius equal to six times the crack depth, the $\text{K}$ at the surface is about 4% higher than the $\text{K}$ for a flat surface. The results of the elastic-plastic analyses show a unique variation of the effective $\text{K}$ (J-integral) along the crack front with a decrease in $\text{K}$ at the surface due to a lack of plane strain constraint and an increase in the effective $\text{K}$ at the maximum depth point with increasing plasticity. Similar behavior was observed for a semielliptical crack. Increasing the strain hardening exponent from 10 to 20 produced similar results with slightly higher effective A's for high applied strains. These results are useful in understanding the fracture behavior of small surface cracks.     

Electrochemical deposition and characterization of cupric oxide thin films

Polycrystalline cupric oxide (CuO) thin films are deposited using an alkaline solution bath employing cathodic electrodeposition method. Thin films are electroplated at various bath temperatures onto conducting indium tin oxide coated glass substrates. The bath temperature effects on the structural, optical and morphological properties of copper oxide films are studied and reported. X-ray diffraction studies revealed mixed phases of monoclinic and cubic for films grown at lower bath temperatures and that the deposited films at temperatures optimized as 75 °C exhibited cubic structure with preferential orientation along a (111) plane. Texture coefficient (T_c) values are calculated for all diffraction lines and the films were highly textured (T_c > 1). The surface morphology and surface roughness are estimated using scanning electron microscopy and atomic force microscopy, respectively and a morphology made up of pyramid shaped grains is presented. Energy dispersive analysis by X-rays revealed that the near stoichiometric CuO thin films are obtained at optimized preparative parameters. The refractive index is calculated using the envelop method. Also, the optical constants of CuO thin films such as complex dielectric constant (ε) and extinction coefficient (k) are also evaluated and reported.