Molecular-beam epitaxy (MBE) is the gold standard for the epitaxial growth of complex oxides with the best material properties as determined by respective figures of merit. Unfortunately, once more than one cation is involved in the material desired, MBE growth often becomes plagued by difficulties in stoichiometry control. Instead of relying on a quartz crystal microbalance to measure the fluxes of the individual molecular beams, which lacks accuracy, or reflection high-energy electron diffraction oscillations of the targeted multication oxide in layer-by-layer growth, which lacks general applicability, here, we describe a canonical approach based on the growth of films of the constituent binary oxides or metals individually for cation flux calibration. This method can calibrate the flux of each molecular beam with an absolute accuracy of ± 1%. After describing the growth parameters of binary oxides or metals enabling the individual fluxes of 39 elements of the periodic table to be determined, we demonstrate the efficacy of this approach by applying it to the growth of the quaternary ferromagnetic metal La 0 . 5 Sr 0 . 5 CoO 3 − δ to achieve films with transport properties rivalling the best reported using thin-film growth techniques providing stoichiometric transfer.

Homologous series are layered phases that can have a range of stoichiometries depending on an index n. Examples of perovskite-related homologous series include (ABO3)nAO Ruddlesden–Popper phases and (Bi2O2) (An−1BnO3n+1) Aurivillius phases. It is challenging to precisely control n because other members of the homologous series have similar stoichiometry and a phase with the desired n is degenerate in energy with syntactic intergrowths among similar n values; this challenge is amplified as n increases. To improve the ability to synthesize a targeted phase with precise control of the atomic layering, we apply the x-ray diffraction (XRD) approach developed for superlattices of III–V semiconductors to measure minute deviations from the ideal structure so that they can be quantitatively eradicated in subsequent films. We demonstrate the precision of this approach by improving the growth of known Ruddlesden–Popper phases and ultimately, by synthesizing an unprecedented n = 20 Ruddlesden–Popper phase, (ATiO3)20AO where the A-site occupancy is Ba0.6Sr0.4. We demonstrate the generality of this method by applying it to Aurivillius phases and the Bi2Sr2Can–1CunO2n+4 series of high-temperature superconducting phases.

Epitaxial perovskite oxide thin films and heterostructures are a highly active materials research topic generating both fundamental and applied interest. This manuscript reports the roles of oxidation kinetics and film deposition rate on the growth of phase-pure complex oxides by molecular-beam epitaxy, one of the premier techniques for these materials, in a regime that is traditionally described as being governed by thermodynamics. It is found that oxidation kinetics on the film surface are surprisingly important for the growth of PbTiO${}_{3}$ and for formulating a simple kinetic theory to interpret experimental observations. The results are also enlightening to predict the conditions for improved growth of BiFeO${}_{3}$ and other complex oxides by MBE, of high interest to the broad community studying oxide films and heterostructures.

We investigate the suitability of an epitaxial CaTiO3 buffer layer deposited onto (100) Si by reactive molecular-beam epitaxy (MBE) for the epitaxial integration of the colossal magnetoresistive material La0.7Sr0.3MnO3 with silicon. The magnetic and electrical properties of La0.7Sr0.3MnO3 films deposited by MBE on CaTiO3-buffered silicon (CaTiO3/Si) are compared with those deposited on SrTiO3-buffered silicon (SrTiO3/Si). In addition to possessing a higher Curie temperature and a higher metal-to-insulator transition temperature, the electrical resistivity and 1/f noise level at 300 K are reduced by a factor of two in the heterostructure with the CaTiO3 buffer layer. These results are relevant to device applications of La0.7Sr0.3MnO3 thin films on silicon substrates.

Single crystalline (0 0 0 1) ZnO films were grown by pulsed-laser deposition on (1 1 1) Si substrates containing thin Sc2O3 buffer layers (1 and 5 nm) which were prepared by molecular-beam epitaxy at 700 degrees C. Both x-ray diffraction and transmission electron microscopy reveal that the ZnO films grown at 240 and 400 degrees C are highly crystalline with good epitaxy. The commonly seen amorphous SiOx layer has been successfully eliminated from the interface between the ZnO/Sc2O3 film and (1 1 1) Si substrate, resulting in improved electrical properties. Rectifying effects are observed in the heterojunction exhibiting a turn-on voltage of 1.08V and an ideality factor of 17.7. The room temperature mobility is 65 cm(2) V (1) s (1). A donor binding energy of 46.7 meV is determined by temperature-dependent photoluminescence measurements.

The effects of film thickness and epitaxial strain on the magnetic properties of commensurate EuO thin films grown on single crystalline (001) yttria-stabilized zirconia (YSZ) and (110) LuAlO3 substrates are presented. Magnetic measurements show a reduction in the Curie temperature (TC) for EuO/YSZ films thinner than ∼10 nm. Additionally, the EuO/LuAlO3 films exhibit a systematically lower TC than the corresponding EuO/YSZ films. This further reduction in TC is attributed to the effect of biaxial tensile strain arising from lattice mismatch: 0.0% for EuO/YSZ and +1.0% for EuO/LuAlO3.

We report the epitaxial integration of phase-pure EuO on both single-crystal diamond and on epitaxial diamond films grown on silicon utilizing reactive molecular-beam epitaxy. The epitaxial orientation relationship is (001) EuO vertical bar vertical bar (001) diamond and [110] EuO vertical bar vertical bar [100] diamond. The EuO layer is nominally unstrained and ferromagnetic with a transition temperature of 68 +/- 2K and a saturation magnetization of 5.5 +/- 0.1 Bohr magnetons per europium ion on the single-crystal diamond, and a transition temperature of 67 +/- 2K and a saturation magnetization of 2.1 +/- 0.1 Bohr magnetons per europium ion on the epitaxial diamond film. (C) 2013 AIP Publishing LLC.

Emergent phenomena, including superconductivity and magnetism, found in the two-dimensional electron liquid (2-DEL) at the interface between the insulators lanthanum aluminate (LaAlO3) and strontium titanate (SrTiO3) distinguish this rich system from conventional 2D electron gases at compound semiconductor interfaces. The origin of this 2-DEL, however, is highly debated, with focus on the role of defects in the SrTiO3, while the LaAlO3 has been assumed perfect. Here we demonstrate, through experiments and first-principle calculations, that the cation stoichiometry of the nominal LaAlO3 layer is key to 2-DEL formation: only Al-rich LaAlO3 results in a 2-DEL. Although extrinsic defects, including oxygen deficiency, are known to render LaAlO3/SrTiO3 samples conducting, our results show that in the absence of such extrinsic defects an interface 2-DEL can form. Its origin is consistent with an intrinsic electronic reconstruction occurring to counteract a polarization catastrophe. This work provides insight for identifying other interfaces where emergent behaviours await discovery.

This chapter contains five sections related to advances in technology and characterization. The first section investigates influence of Ti top electrodes on the oxidation state of epi-taxially grown STO thin films and the corresponding resistive switching devices. The second section shows comparison of work diode- and CO2-laser heater versions. The third section reviews the influence of ALD processing and different top electrodes on the structural, morphological and electrical properties of ZrO2. The fourth section views the resistance switching characteristic of Nb2O5 thin films integrated into Pt/Nb2O5/Ti/Pt micro cross bar structures on Si/SiO2 substrates. The fifth section considers the investigations of CDW in Dy5Ir4Si10 at different temperatures using transmission electron microscopy (TEM) techniques including electron diffraction and dark-field imaging. Controlled Vocabulary Terms electron diffraction; switching; thin films; transmission electron microscopy

We report the growth of single-phase (0001)-oriented epitaxial films of the purported electronically driven multiferroic, LuFe2O4, on (111) MgAl2O4, (111) MgO, and (0001) 6H-SiC substrates. Film stoichiometry was regulated using an adsorption-controlled growth process by depositing LuFe2O4 in an iron-rich environment at pressures and temperatures where excess iron desorbs from the film surface during growth. Scanning transmission electron microscopy reveals reaction-free film-substrate interfaces. The magnetization increases rapidly below 240 K, consistent with the paramagnetic-to-ferrimagnetic phase transition of bulk LuFe2O4. In addition to the ∼0.35 eV indirect band gap, optical spectroscopy reveals a 3.4 eV direct band gap at the gamma point.

Low temperature magneto-transport properties and electron dephasing mechanisms of phosphorus-doped ZnO thin films grown on (1 1 1) Si substrates with Lu2O3 buffer layers using pulsed laser deposition were investigated in detail by quantum interference and weak localization theories under magnetic fields up to 10 T. The dephasing length follows the temperature dependence with an index p≈1.6 at higher temperatures indicating electron–electron interaction, yet becomes saturated at lower temperatures. Consistent with photoluminescence measurements and the multi-band simulation of the electron concentration, such behavior was associated with the dislocation densities obtained from x-ray diffraction and mobility fittings, where charged edge dislocations acting as inelastic Coulomb scattering centers were affirmed responsible for electron dephasing. Owing to the temperature independence of the dislocation density, the phosphorus-doped ZnO film maintained a Hall mobility of 4.5 cm2 V−1 s−1 at 4 K.

Electron energy loss spectroscopy (EELS) in a new generation of aberration-corrected electron microscopes provides direct images of the local physical and electronic structure of a material at the atomic scale. The sensitivity and resolution can extend to imaging single dopant atoms or vacancies in their native environments. The detection and control of interface defects using EELS, closely-coupled with atomically-precise growth methods, has enabled the realization of interface-stabilized emergent ground states, including a 2D metal at the LaTiO3/SrTiO3 interface; a 2D superconductor between a LaAlO3 and SrTiO3; and, by eliminating extended 2D defects, ferromagnetic manganites a few unit cells thick - well below the widely-assumed critical thickness for ferromagnetism and conductivity in manganite systems. In each case, the detection and control of defects has proven crucial to distinguishing between intrinsic and extrinsic interface effects.This is well illustrated at the LaAlO3/SrTiO3 interface. Controlled Vocabulary Terms electron energy loss spectra; electron microscopes; exotic atoms; ferromagnetism

The effect of lutetium doping on the structural, electronic, and magnetic properties of epitaxial EuO thin films grown by reactive molecular-beam epitaxy is experimentally investigated. The behavior of Lu-doped EuO is contrasted with doping by lanthanum and gadolinium. All three dopants are found to behave similarly despite differences in electronic configuration and ionic size. Andreev reflection measurements on Lu-doped EuO reveal a spin-polarization of 96% in the conduction band, despite non-magnetic carriers introduced by 5% lutetium doping.

Rare earth doping is a standard, yet experimentally poorly understood method to increase the Curie temperature (TC) of the ferromagnetic semiconductor EuO. Here, we report on the charge carrier density (n) and the TC of commonly used 4.2 at. % Gd-doped EuO films grown by molecular-beam epitaxy on (110) oriented YAlO3 substrates at various substrate temperatures (Tsub). Increasing Tsub leads to a decrease in n and TC. For high substrate temperatures the Gd-doping is rendered completely inactive: n and TC drop to the values of undoped EuO.

Insulated gate n-channel enhancement mode InGaAs field effect transistors with the GdScO 3 high-k dielectric have been fabricated and studied. The low frequency noise was high indicating a high interface density of traps. Trap density and its dependence on the gate voltage have been extracted from the noise and conductance measurements.

Ferroelectric domain orientations have been mapped using piezo-force microscopy, allowing the calculation and statistical analysis of interfacial polarization angles, the head-to-tail or head-to-head configuration, and any cross-coupling terms. Within 1 µm2 of an epitaxial (001)p-oriented BiFeO3 film, there are >40 µm of linear domain boundary based on over 500 interfaces. 71° domain walls dominate the interfacial polarization angles, with a 2:1 preference for uncharged head-to-tail versus charged head-to-head boundary types. This mapping technique offers a unique perspective on domain boundary distributions, important for ferroelectric and multiferroic applications where domain wall parameters are critical.