The growth of single crystal films of silver on rocksalt by sputtering

Thin films of silver on rocksalt have been prepared by diode sputtering in an argon discharge. Deposition rate, substrate temperature, and film thickness have been varied, and dependence of orientation on these parameters has been studied. Within a deposition rate range of 0.1 to 1.15Å/sec, films have been grown with (100) [110]_Ag / / (100) [110]_NaCl orientation, at temperatures in the range –35 to 0° C. Higher rates required higher temperatures. Films giving these results were all 200 Å in thickness. A thickness dependence of orientation has been observed for films below 120 Å in thickness.The above results are discussed in terms of the effect of arrival energy of the sputtered material at the substrate. The results of calculations, on the effect of gas pressure on the arrival energy, are presented and it is shown that, at 10^–2 torr, up to 15% of the arriving atoms will have energies above 0.6 eV. That the observed rate, temperature, and thickness dependence of epitaxy are due to surface cleaning and penetration effects caused by the energy of arrival of the atoms is shown to be possible.The effect of charged particle bombardment of the substrate is also considered. It is shown that this may also be an important parameter affecting the growth.     

The effect of sulphur-terminated GaAs substrates on the MOVPE growth of CuGaS2 thin films

In this study, various CuGaS₂ layers were grown on GaAs (001) substrates using metalorganic vapour phase epitaxy, for the purpose of studying the effect of sulphur-termination of the substrate on layer quality. The resultant films were investigated using X-ray diffractometry, and transmission electron microscopy, with high-resolution transmission electron microscopy providing additional insights into crystallite growth on the control substrates. This paper will demonstrate that sulphur-termination limits substrate degradation. In the absence of sulphur-termination, atypical three-dimensional MOVPE growth is observed, with epitaxial crystallites varying in size from 10 nm to 200 nm. Substrate degradation inhibits lateral growth at the interface resulting in amorphous regions, cavities, and epitaxial crystallites demonstrating overgrowth into mushroom-like structures.     

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.     

Morphology of TiN thin films grown on SiO2 by reactive high power impulse magnetron sputtering

Thin TiN films were grown on SiO₂ by reactive high power impulse magnetron sputtering (HiPIMS) at a range of temperatures from 45 to 600 °C. The film properties were compared to films grown by conventional dc magnetron sputtering (dcMS) at similar conditions. Structural characterization was carried out using X-ray diffraction and reflection methods. The HiPIMS process produces denser films at lower growth temperature than does dcMS. Furthermore, the surface is much smoother for films grown by the HiPIMS process. The [200] grain size increases monotonically with increased growth temperature, whereas the size of the [111] oriented grains decreases to a minimum for a growth temperature of 400 °C after which it starts to increase with growth temperature. The [200] crystallites are smaller than the [111] crystallites for all growth temperatures. The grain sizes of both orientations are smaller in HiPIMS grown films than in dcMS grown films.     

Epitaxial growth of SrTiO3 films with different orientations on TiN buffered Si(001) by pulsed laser deposition

Epitaxial SrTiO₃ (STO) films have been grown on TiN buffered Si(001) by pulsed laser deposition. The TiN layer was in situ deposited at 540, 640 or 720°C whereas the STO film was grown at a fixed temperature of 640°C. We have studied the effect of the growth temperature of TiN on the epitaxial relationship of STO/TiN heterostructures. It is found that for TiN grown at 540 or 640°C the epitaxial relationship is 001STO 001TiN, and for TiN grown at 720°C it changes to (101)STO (001)TiN and [ 01]STO [1 0]TiN (or [ 01]STO [110]TiN). This change of relationship is accompanied by a sharp reduction in the out-of-plane lattice constant of the TiN layer. Fourier transform infrared spectra show that the longitudinal optic modes are active for all the STO films, but the absorption peak associated with the transverse optic mode is observed only in the (101) oriented STO films.     

Epitaxial growth and electrical measurement of single crystalline Pb(Zr0.52Ti0.48)O3 thin film on Si(001) for micro-electromechanical systems

We report in this work the epitaxial growth and the electrical characteristics of single crystalline Pb(Zr_0.52Ti_0.48)O₃ (PZT) thin film on SrTiO₃(STO)-buffered Si(001) substrate. The STO buffer layer deposited by molecular beam epitaxy allows a coherent oxide/Si interface leading enhanced PZT crystalline quality. 70 nm-thick PZT (52:48) layer was then grown on STO/Si(001) by sol-gel method. X-ray diffraction demonstrates the single crystalline PZT film on Si substrate in the following epitaxial relationship: [110] PZT (001)//[110] STO (001)//[100] Si (001). The macroscopic electrical measurements show a hysteresis loop with memory window of 2.5 V at ± 7 V sweeping range and current density less than 1 μA/cm² at 750 kV/cm. The artificial domains created by piezoresponse force microscopy with high contrast and non-volatile properties provide further evidence for the excellent piezoelectric properties of the single crystalline PZT thin film.     

A computational study of kinetic phase diagrams for CoPt alloy films during epitaxial growth

We have studied the kinetic processes of the epitaxial growth for CoPt alloy films using the master equation method. The kinetic phase diagrams of CoPt alloy films which show the phase formation conditions during the epitaxial growth are determined. From the kinetic phase diagrams, we find that the [001] ordered structure is much easy to be grown at high temperature while the [100] ordered structure is easy to be grown at low temperature although both the [001] and [100] ordering could be the equilibrium ground states. The atomic deposition, ordering and surface segregation lead to a rich variety of phases in epitaxial growth. The surface segregation is found to enhance the [001] ordering and leads to the formation of the [001] ordered phase at high temperature.     

Laser molecular beam epitaxy growth and properties of SrTiO3 thin films for microelectronic applications

Dielectric SrTiO₃ thin films were deposited on LaAlO₃ and Si substrates using laser molecular beam epitaxy. The correlations between the deposition parameters of SrTiO₃ thin films, their structural characteristics, and dielectric properties were studied. The conditions for achieving epitaxial SrTiO₃ thin films were found to be limited to deposition conditions such as deposition temperature. We show that the SrTiO₃ films with single (110) orientation can be grown directly on Si substrates. The nature of epitaxial growth and interfacial structures of the grown films were examined by various techniques, such as Laue diffraction and X-ray photoelectron spectroscopy. The SrTiO₃/Si interface was found to be epitaxially crystallized without any SiO₂ layer. Furthermore, we have measured dielectric properties of the grown SrTiO₃ multilayer suitable for tunable microwave device. A large tunability of 74.7%, comparable to that of SrTiO₃ single-crystal, was observed at cryogenic temperatures. Such STO thin films will be very promising for the development of microelectronic device applications.     

Fully strained low-temperature epitaxy of TiN/MgO(001) layers using high-flux, low-energy ion irradiation during reactive magnetron sputter deposition

Epitaxial TiN layers, 0.3 μm thick, are grown on MgO(001) in the absence of applied substrate heating using very high flux, low-energy (below the lattice atom displacement threshold), ion irradiation during reactive magnetron sputter deposition in pure N₂ discharges. High-resolution x-ray diffraction, reciprocal lattice maps, and transmission electron microscopy analyses reveal that the TiN(001) films grow with an (001)_TiN||(001)_MgO and [100]_TiN||[100]_MgO orientation relationship to the substrate. The layers are fully coherent with no detectable misfit dislocations. For comparison, TiN/MgO(001) films grown at temperatures of 700-850 °C under similar conditions, but with no intentional ion irradiation, are fully relaxed with a high misfit dislocation density. Thus, the present results reveal that intense low-energy ion irradiation during film growth facilitates high adatom mobilities giving rise to low-temperature epitaxy, while the low growth temperature quenches strain-induced relaxation and suppresses misfit dislocation formation.     

A systematic study on the growth of PZNT films by LPE method

Liquid phase epitaxy (LPE) was used to grow (1−x)Pb(Zn_1/3Nb_2/3)O₃−xPbTiO₃ (PZNT) films on different substrates. The morphology and epitaxial relationship of PZNT films with these substrates were investigated by optical microscopy and XRD. It was found that PZNT grains on planes of (001) MgO, (001) LaAlO₃ (LAO) and two specific planes of SrTiO₃ (STO), i.e. (110) or (111), distribute randomly and show no evident epitaxial relationship with these substrates. However PZNT films on (001) STO substrates exhibit very encouraging in-plane epitaxial relation: [100](001)_PZNT // [100](001)_STO, which was observed directly by OM, SEM and further confirmed by X-ray diffraction.     

Hot-wire chemical vapor deposition for epitaxial silicon growth on large-grained polycrystalline silicon templates

We investigate low-temperature epitaxial growth of thin silicon films by HWCVD on Si [1 0 0] substrates and polycrystalline template layers formed by selective nucleation and solid phase epitaxy (SNSPE). We have grown 300-nm thick epitaxial layers at 300 °C on silicon [1 0 0] substrates using a high H₂:SiH₄ ratio of 70:1. Transmission electron microscopy confirms that the films are epitaxial with a periodic array of stacking faults and are highly twinned after approximately 240 nm of growth. Evidence is also presented for epitaxial growth on polycrystalline SNSPE templates under the same growth conditions.     

Structural and dielectric properties of (001) and (111)-oriented BaZr0.2Ti0.8O3 epitaxial thin films

We have grown and characterized BaZr_0.2Ti_0.8O₃ (BZT) epitaxial thin films deposited on (001) and (111)-oriented SrRuO₃-buffered SrTiO₃ substrates by pulsed laser deposition. Structural and morphological characterizations were performed using X-ray diffractometry and atomic force microscopy, respectively. A cube-on-cube epitaxial relationship was ascertained from the θ-2θ and φ diffractograms in both (001) and (111)-oriented films. The (001)-oriented films showed a smooth granular morphology, whereas the faceted pyramid-like crystallites of the (111)-oriented films led to a rough surface. The dielectric response of BZT at room temperature was measured along the growth direction. The films were found to be ferroelectric, although a well-saturated hysteresis loop was obtained only for the (001)-oriented films. High leakage currents were observed for the (111) orientation, likely associated to charge transport along the boundaries of its crystallites. The remanent polarization, coercive field, dielectric constant, and relative change of dielectric permittivity (tunability) of (111)-oriented BZT were higher than those of (001)-oriented BZT.     

Epitaxial growth of rhenium with sputtering

We have grown epitaxial Rhenium (Re) (0001) films on α-Al₂O₃ (0001) substrates using sputter deposition in an ultra high vacuum system. We find that better epitaxy is achieved with DC rather than with RF sputtering. With DC sputtering, epitaxy is obtained with the substrate temperatures above 700 °C and deposition rates below 0.1 nm/s. The epitaxial Re films are typically composed of terraced hexagonal islands with screw dislocations, and island size gets larger with high temperature post-deposition annealing. The growth starts in a three dimensional mode but transforms into two dimensional mode as the film gets thicker. With a thin (∼2 nm) seed layer deposited at room temperature and annealed at a high temperature, the initial three dimensional growth can be suppressed. This results in larger islands when a thick film is grown at 850 °C on the seed layer. We also find that when a room temperature deposited Re film is annealed to higher temperatures, epitaxial features start to show up above ∼600 °C, but the film tends to be disordered.     

Residual crystallinity of vapor-deposited tin films

Using transmission electron microscopy and selected-area electron diffraction techniques, the residual crystallinity of vapor-deposited tin thin films has been investigated. At substrate temperatures above about 0.8T_m, liquid-like particles were observed to be single crystals, with no evidence of grain boundaries or related crystallographic inhomogeneities. A significant portion of the single-crystal particles exhibited epitaxial features, and they appeared to have solidified by a liquid-solid phase transformation beginning at the particle-substrate interface and propagating in the [001] direction, with the (00$\text{1}$) plane facing the (001) NaCl substrate. The observation of crystal facets supports this model. For substrate temperatures of approximately 0.7T_m or below, the tin films were composed of island structures. An examination of the crystallographic and morphological features of the tin films suggests a coalescence mechanism consistent with that outlined by Pocza. For substrate temperatures greater than 0.8T_m, coalescence is dominated by liquid drops with liquid drops. Below 0.8T_m, the mechanism shifts from one of liquid drops with crystallites to one dominated primarily by the coalescence of crystallites with crystallites below 0.6T_m.     

Preparation of epitaxial DyFeO3 thin films and magnetodielectric coupling

Multiferroic DyFeO₃ thin films deposited on (001) Nb-doped SrTiO₃ (NSTO) substrates are prepared by pulsed laser deposition. We demonstrate the epitaxial deposition of DyFeO₃ thin films on the substrates with the DyFeO₃(001)//NSTO(001) out-of-plane and DyFeO₃[100]//NSTO[110] in-plane epitaxial relationship. In addition, the weak ferromagnetism and significant magnetodielectric coupling effect at low temperature are revealed. It is indicated that the DyFeO₃ thin films have very different properties from the DyFeO₃ single crystals in term of multiferroicity.     

Preparation of [001]- and [107]-Oriented Epitaxial YbBa2Cu4O8 Films Prepared by Coating-Pyrolysis Process

YbBa ₂ Cu ₄ O ₈ (Yb124) films were prepared on SrTiO ₃ (001) and SrTiO ₃ (110) substrates by coating-pyrolysis process at ambient pressure, and the alignments of these films were investigated by XRD -2 scanning and XRD pole-figure analysis. Films prepared on SrTiO ₃ (001) consisted of almost single-phase [001]-oriented epitaxial Yb124. On the other hand, films on SrTiO ₃ (110) consisted of [107]-oriented epitaxial Yb124 and other impurity phases, one of which was considered to be so-called other perovskite phase.     

Growth of SrTiO3 thin films on LaAlO3(001) substrates; the influence of growth temperature on composition, orientation, and surface morphology

SrTiO₃ films have been grown on LaAlO₃(001) single crystal substrates using rf-sputtering. The substrates were held at temperatures ranging from 100 to 850°C. For growth temperatures as low as 350°C epitaxial growth is observed. Below 350°C the films are polycrystalline and three different orientations (100), (110), and (111) can be observed using X-ray diffraction. Atomic force microscopy shows that films deposited at temperatures below 350°C and above 650°C are smooth while the surfaces of the films made at intermediate temperatures are rough and faceted. As growth temperatures decrease below 250°C, the films show decreasing amount of Sr.     

Ferroelectric properties of epitaxial Bi3.15Nd0.85Ti3O12 films on SiO2/Si using biaxially oriented MgO as templates

High quality epitaxial Bi_3.15Nd_0.85Ti₃O₁₂ (BNT) thin films with thicknesses from 30 to 80 nm have been integrated on SiO₂/Si substrates. MgO templates deposited by ion-beam-assisted deposition and SrRuO₃ (SRO) buffer layers processed by pulsed laser deposition have been used to initiate the epitaxial growth of BNT films on the amorphous SiO₂/Si substrates. The structural and ferroelectric properties were investigated. Microstructural studies by X-ray diffraction and transmission electron microscopy revealed high quality crystalline with an epitaxial relationship of (001)_BNT||(001)_SRO||(001)_MgO and [100]_BNT||[110]_SRO||[110]_MgO. A ferroelectric hysteresis loop with a remanent polarization of 3.1 μC/cm² has been observed for a 30 nm thick film. The polarization exhibits a fatigue-free characteristic up to 1.44 × 10¹⁰ switching cycles.     

Gas phase particle formation and elimination on Si (100) in low temperature reduced pressure chemical vapor deposition silicon-based epitaxial layers

Gas phase particle formation and elimination in silicon epitaxial layers grown on Si (100) substrates using reduced pressure chemical vapor deposition at low temperatures (< 600 °C) are investigated. High-order silane precursors (Si_nH_2n + 2; n = 3, n > 3) are useful for high growth rate epitaxy at low temperature. However, particulates are observed on the surface of the epitaxial layers grown with high-order silanes. These particulates are attributed to gas phase particles. As atomically smooth epitaxial films are desired, the elimination of gas phase particles is required. Cyclical deposition and etch process and/or low pressure deposition enables atomically smooth SiCP epitaxial films with a high-order silane.     

Microstructure and secondary phases in epitaxial LaBaCo_2O_(5.5 + δ) thin films

Aberration-corrected scanning transmission electron microscopy was employed to investigate the microstructures and secondary phases in LaBaCo_2O_(5.5 + δ)(LBCO) thin films grown on SrTiO_3(STO) substrates. The as-grown films showed an epitaxial growth on the substrates with atomically sharp interfaces and orientation relationships of [100]_(LBCO)//[100]_(STO)and(001)_(LBCO)//(001)_(STO). Secondary phases were observed in the films, which strongly depended on the sample fabrication conditions. In the film prepared at a temperature of 90℃, nano-scale CoO pillars nucleated on the substrate, and grew along the [001]direction of the film. In the film grown at a temperature of 1000℃, isolated nano-scale Co_3O_4 particles appeared, which promoted the growth of {111} twinning structures in the film. The orientation relationships and the interfaces between the secondary phases and the films were illustrated, and the growth mechanism of the film was discussed.