Masashi Kurosawa

Bio: Masashi Kurosawa is an academic researcher from Nagoya University. The author has contributed to research in topics: Crystallization & Annealing (metallurgy). The author has an hindex of 20, co-authored 116 publications receiving 1299 citations. Previous affiliations of Masashi Kurosawa include Kyushu University & Japan Society for the Promotion of Science.

Orientation-controlled Si thin films on insulating substrates by Al-induced crystallization combined with interfacial-oxide layer modulation

Abstract: Orientation-controlled Si films on transparent insulating substrates are strongly desired to achieve high-efficiency thin-film solar cells. We have developed the interfacial-oxide layer modulated Al-induced low temperature (<450 °C) crystallization technique, which enables dominantly (001) or (111)-oriented Si films with large grains (20–100 μm). These results are qualitatively explained on the basis of a model considering the phase transition of the interfacial Al oxide layers. This process provides the orientation-controlled Si templates on insulating substrates, which enables successive high quality epitaxial growth necessary for advanced Si thin-film solar cells.

Germanene Epitaxial Growth by Segregation through Ag(111) Thin Films on Ge(111).

Abstract: Large-scale two-dimensional sheets of graphene-like germanium, namely, germanene, have been epitaxially prepared on Ag(111) thin films grown on Ge(111), using a segregation method, differing from molecular beam epitaxy used in previous reports. From the scanning tunneling microscopy (STM) images, the surface is completely covered with an atom-thin layer showing a highly ordered long-range superstructure in wide scale. Two types of protrusions, named hexagon and line, form a (7√7 × 7√7)R19.1° supercell with respect to Ag(111), with a very large periodicity of 5.35 nm. Auger electron spectroscopy and high-resolution synchrotron radiation photoemission spectroscopy demonstrate that Ge atoms are segregated on the Ag(111) surface as an overlayer. Low-energy electron diffraction clearly shows incommensurate “(1.35 × 1.35)”R30° spots, corresponding to a lattice constant of 0.39 nm, in perfect accord with close-up STM images, which clearly reveal an internal honeycomb arrangement with corresponding parameter and ...

Highly (111)-oriented Ge thin films on insulators formed by Al-induced crystallization

Abstract: (111)-oriented Ge thin films on insulators are essential for advanced electronics and photovoltaic applications. We investigate Al-induced crystallization of amorphous-Ge films (50-nm thickness) on insulators focusing on the annealing temperature and the diffusion controlling process between Ge and Al. The (111)-orientation fraction of the grown Ge layer reaches as high as 99% by combining the low-temperature annealing (325 °C) and the native-oxidized Al (AlOx) diffusion-control layer. Moreover, the transmission electron microscopy reveals the absence of defects on the Ge surface. This (111)-oriented Ge on insulators promises to be the high-quality epitaxial template for various functional materials to achieve next-generation devices.

Nucleation-controlled gold-induced-crystallization for selective formation of Ge(100) and (111) on insulator at low-temperature (∼250 °C)

Abstract: Selective formation of Ge(100) and (111) on amorphous-insulator at low-temperatures (∼250 °C) is realized through gold-induced-crystallization using a-Ge/Au/SiO2 stacked-structures by combining interface-energy-modulation of substrates. Introduction of thin-Al2O3 layers (∼7 nm thickness) at a-Ge/Au interfaces enables large-grain (≥20 μm) Ge(111) formation, which is speculated to be due to suppression of random bulk-nucleation and domination of (111)-oriented interface-nucleation on SiO2. To examine this speculation, Al2O3-covered substrates are employed. This results in formation of Ge(100), due to energetically favorable (100)-oriented interface-nucleation on Al2O3. Consequently, large-grain (≥20 μm) Ge(100) and (111) are achieved on amorphous-insulators at 250 °C. This technique is very useful to realize flexible-electronics.

Recent Advances in Two-Dimensional Materials beyond Graphene

Abstract: The isolation of graphene in 2004 from graphite was a defining moment for the “birth” of a field: two-dimensional (2D) materials In recent years, there has been a rapidly increasing number of papers focusing on non-graphene layered materials, including transition-metal dichalcogenides (TMDs), because of the new properties and applications that emerge upon 2D confinement Here, we review significant recent advances and important new developments in 2D materials “beyond graphene” We provide insight into the theoretical modeling and understanding of the van der Waals (vdW) forces that hold together the 2D layers in bulk solids, as well as their excitonic properties and growth morphologies Additionally, we highlight recent breakthroughs in TMD synthesis and characterization and discuss the newest families of 2D materials, including monoelement 2D materials (ie, silicene, phosphorene, etc) and transition metal carbide- and carbon nitride-based MXenes We then discuss the doping and functionalization of 2

Scattering of light in crystals

Abstract: Since its discovery1, early in 1928, the scattering of light with altered frequency has been investigated in many crystals, and much valuable information has been accumulated. The significance of the results and their relation to theories of solid state are clearly matters of great interest.

Direct Measurement of Room-Temperature Nondiffusive Thermal Transport Over Micron Distances in a Silicon Membrane

Abstract: The "textbook" phonon mean free path of heat carrying phonons in silicon at room temperature is ∼40 nm. However, a large contribution to the thermal conductivity comes from low-frequency phonons with much longer mean free paths. We present a simple experiment demonstrating that room-temperature thermal transport in Si significantly deviates from the diffusion model already at micron distances. Absorption of crossed laser pulses in a freestanding silicon membrane sets up a sinusoidal temperature profile that is monitored via diffraction of a probe laser beam. By changing the period of the thermal grating we vary the heat transport distance within the range ∼1-10 μm. At small distances, we observe a reduction in the effective thermal conductivity indicating a transition from the diffusive to the ballistic transport regime for the low-frequency part of the phonon spectrum.