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Ga-incorporated ZnSnAs [ABSTRACT FROM AUTHOR]

Abstract: Ternary ZnSnAs2 thin films heavily doped with nominal 10 and 20% Mn content on InP (001) substrates are grown using low-temperature molecular beam epitaxy and their magnetic and transport properties are investigated for the first time. It is found that the Mn-doped ZnSnAs2 thin films are pseudomorphically grown on nearly lattice-matched InP (001) substrates, and a trace amount of secondary phase MnAs formation is observed by high-resolution X-ray diffraction (HR-XRD) measurements. Magnetization measurements on Mn-doped ZnSnAs2 thin films reveal that the Curie temperature is around 334K. Nominal magnetic moments per Mn atom measured from the saturation magnetization of hysteresis loops at 5K have been estimated as 5.28 and 4.17μB for 10% and 20% Mn-doped ZnSnAs2 thin films, respectively. We have found from Hall effect measurements that the 10% and 20% Mn-doped ZnSnAs2 films exhibit n-type conduction, in contrast to p-type conduction in ZnSnAs2 doped with less than 10% Mn. This is likely related to the presence of a certain amount of Mn interstitials or Mn3+ substitution on Zn site in the samples. [Copyright &y& Elsevier]

Abstract: For the purpose of investigating their structural and optical properties, GaSb thin films and GaSb/AlSb multiple quantum well (MQW) structures were grown on Si(111) substrates. A GaSb/AlSb MQW structure was also grown on Si(001) substrate as a control sample. Surface morphologies and a XRD measurements of GaSb films grown on Si(111) substrates showed that the GaSb film with a 5 nm thick AlSb initiation layer has good crystal quality. Observation of the RHEED patterns of both MQWs suggests that both GaSb films are under tensile strain at growth temperature. In-plane XRD measurement of MQW on Si(111) showed that the (111) face of the GaSb film is aligned to the Si(111) surface upon rotation by 30°. Photoluminescence (PL) spectra consisting of two peaks at 1250∼1400 nm were observed for both MQWs. [Copyright &y& Elsevier]

MnAs thin films were grown by low-temperature molecular beam epitaxy on semi-insulating GaAs(1 0 0) substrates under varying growth parameters, including the As4/Mn flux ratio and Mn beam equivalent pressure. When the As4/Mn flux ratio was set at 1–1.2, the Mn–As blocks were formed, and an increasing As4/Mn flux ratio resulted in a growth of αMnAs with the growth direction of [1¯ 1 0 1] and the the mirror-like surface. Under restricted growth conditions, ferromagnetic hexagonal αMnAs layers were first prepared on GaAs(1 0 0) substrates at 250 °C, and orthorhombic Mn3As2 blocks were subsequently formed on the MnAs layers. [Copyright &y& Elsevier]

The structural, magnetic, and electrical properties of InMnAs thin films were investigated to elucidate their ferromagnetism for potential applications in InP-based spintronics and magneto-optical integrated circuits. The films were prepared on InP substrates by molecular beam epitaxy at growth temperatures of 220–280 °C without further annealing. Except for the 220 °C-grown sample, the films showed ferromagnetism at room temperature. We found that the room-temperature ferromagnetism was predominantly caused by the existence of hexagonal MnAs clusters embedded in a homogeneous InMnAs matrix (InMnAs:MnAs system). High-resolution transmission electron microscope images revealed that the MnAs nanoclusters formed either elongated or round structures in the InMnAs host matrix. The experimental results indicate that the mixed systems of hexagonal MnAs embedded in InMnAs may provide potential ferromagnetic building blocks for InP-based spintronics. [ABSTRACT FROM AUTHOR]

Abstract: The detailed crystalline structure of molecular beam epitaxially grown MnAs thin films on InP(001) substrate has been investigated using high resolution X-ray diffraction techniques. Reciprocal space mapping of the MnAs/InP(001) samples indicates that the MnAs has a cubic zinc-blende (zb) structure with the epitaxial relationship zb-MnAs[110]|InP[110]. The lattice constant of zb-MnAs is ∼6.06Å. The MnAs lattice is relaxed and is mosaic-like likely due to large lattice mismatch between the film and InP substrate. The isotropic nature of the magnetic properties supported our conjecture that the MnAs epitaxial film under study has indeed a cubic structure. [Copyright &y& Elsevier]

Abstract: GaSb thin films have been grown on Si(111) substrates by molecular beam epitaxy (MBE), using an Sb template as an initiation layer. The film's crystal properties were investigated by in situ reflection high energy electron diffraction (RHEED), atomic force microscope (AFM), X-ray reciprocal space mapping (RSM) and X-ray diffraction (XRD). RSMs around Si and GaSb 224 reciprocal lattice points indicated that the GaSb thin film grown on the Sb template is nearly unstrained, in contrast to that grown on an AlSb initiation layer which is under tensile strain. The extra peaks on the XRD profiles can be assigned to {224} diffraction originating from a sub-domain region that corresponds to the region rotated by 180° with respect to the fundamental domain of epitaxial film. The very weak intensity of the extra peaks suggests that using the Sb template is an effective way to suppress sub-domain generation in the epitaxial film, resulting in a higher quality GaSb thin film on Si(111) substrates. The spotty RHEED patterns observed were analyzed as a superposition of zinc-blende type diffraction spots on the plane and plane, indicating that the GaSb quantum dots at the initial growth stage are not randomly orientated polycrystalline structures but a two-domain structure with zinc-blende type crystals. [Copyright &y& Elsevier]

Abstract: We have prepared Ge0.92Mn0.08 thin films by molecular beam epitaxy (MBE) on semi-insulating (001) GaAs substrates and investigated their transport and magnetic properties. We have found out that the resulting properties of the thin films are highly dependent on the substrate temperature T s. The sample grown at T s=130°C exhibited a pronounced negative magnetoresistance and anomalous Hall effect even up to room temperature most probably due to the presence of substitutional Mn in the Ge host matrix and the formation of the Ge5Mn3 phase. Because these phenomena were not detected for samples grown above 130°C, we believe that these are due to the T s dependence of Mn distribution in Ge0.92Mn0.08 thin films and the degree of the interdiffusion of Ge, Ga and As atoms at the Ge0.92Mn0.08/GaAs interface. [Copyright &y& Elsevier]