After the discovery of graphene prepared by peeling graphite off using scotch tape, many methods are proposed, such as thermal decomposition of silicon carbide (SiC), and chemical vapor deposition (CVD) method. The CVD method seems like to be most popular among those methods. However, the CVD requires metal catalyst (Cu, Ni), and films deposited on such metals are required to transfer onto insulating substrates for device applications. Another method we have previously reported employs pencils and paper.
Paper sheet drown using a lead pencil was irradiated by both femtosecond laser and laser cutter (consumer product, a few hundred dollars), and graphitic materials remain on the paper sheet [1]. In this presentation, another method using pulsed laser deposition (PLD) in carbon dioxide[2] will be proposed, and we estimated an adsorption energy between clusters and substrate surface for choice of substrates. A molecular dynamics was used to estimate the adsorption energy[3].
[1] Kaneko et. al. Jpn. J. Appl. Phys. 55 (2016) 01AE24.
[2] Kaneko et. al. ACS Omega 2 (2017) 1523.
[3] Kaneko et. al. Sci. Rep. 12(2022)15809.
We report periodic nanostructure on solid material irradiated by scanning continuous wave (CW) laser. Long
periodic nano strip grating lines (nano-SGL) formed, not in a spot, but along the trace of the beam scan, literally
parallel to each other with a
at trough between the strip lines. The period of nanostructure was varied with
the laser power between 500 nm and 800 nm, which equals to wavelengths used for laser scanning of green and
infrared lasers. Thermal simulation and Raman spectra indicated the temperature of target exceeded the melting
temperature to form the periodic nanostructure on target materials.
We fabricated indium tin oxide (ITO) thin films on nanoimprinted glass substrates using pulsed laser deposition (PLD).
The nanoimprinted glass substrate was prepared by thermal nanoimprint using an atomically stepped sapphire (α-Al2O3
single crystal) mold. Two kinds of sapphire molds were employed, one with a single step about 0.2 nm high and the
other with a bunched step about 2 nm high. The surface morphology of the stepped sapphire mold was successfully
transferred to the glass surface in an atomic scale. The nanoimprinted glass had a regular nanostepped pattern; one had a
step height of about 0.2 nm and step separation of about 100 nm, the other had a step height of about 2 nm and step
separation of about 1 μm. The ITO films were deposited at room-temperature (RT) or 200°C on the nanoimprinted glass
substrates and on the non-patterned commercial glass for comparison. The ITO films deposited at RT were post-annealed
for further crystallization. The surface of the ITO thin films deposited on the nanoimprinted glass well reflected the
nanopattern of the glass substrate surface. Preferential crystalline orientation of the ITO thin films was achieved on the
nanoimprinted glass substrates. The resistivity of ITO thin films deposited on the nanoimprinted glass was lower than
that on the commercial glass, which was probably due to the higher crystal orientation of the films grown on the
nanoimprinted glass surfaces.
The nanoscale growth control of functional ceramic thin films was examined by our originally developed technique,
which was based on the nanoscale substrate engineering as well as atomic layer control via laser molecular beam epitaxy
(laser-MBE). The atomically controlled surface of the substrate such as the ultrasmooth sapphire (single-crystal Al2O3)
substrate with atomic steps and atomically smooth terraces was found to enhance atomically layer-by-layer growth as
well as self-assembled nucleation along the atomic steps. The novel epitaxial growths could be attained on the physically
or chemically controlled substrates, that is, (1) termination-regulated molecular layer-by-layer epitaxy, (2) step-decoration
epitaxy resulting in the nanowire or nanodots, (3) room-temperature epitaxial growth of AlN, and (4) self-organized
formation of the nanogroove-striped pattern on the film surface.
Interface structures of SrTiO3/Si were investigated systematically using combinatorial method with growth temperature gradient in pulse laser deposition and cross sectional high resolution transmission electron microscopy . A combinatorial pulse laser deposition with growth temperature gradient system was employed to grow SrTiO3 on Si (100) with various temperatures and oxygen pressures. A high throughput thin foil fabrication system, which is so called micro sampling system, was employed to fabricate thin foils for cross sectional high resolution transmission electron microscope observation. As a result, we have observed a never reported amorphized SrTiO3 layer in the crystalline SrTiO3 thin films grown on Si (100) at growth temperatures above 600°C. From the growth condition dependence studies on the formation of amorphized SrTiO3 layers and the electron energy loss spectroscopy measurements, the origin of the amorphization was concluded as an effect of diffusion of Si from substrate. This is the first observation of a diffusion induced amorphization phenomenon in the crystalline SrTiO3 thin films grown on Si (100). Our results show that at higher growth temperatures, the interface structures of SrTiO3/Si are dominated by the diffusion of Si from the Si substrates.
A combinatorial methodology was employed to investigate oxide materials/semiconductor interfaces for future devices. For this purpose, a temperature gradient pulsed laser deposition to find optimum growth condition and transmission electron microscopy for structure and composition analysis were used. Newly proposed the "micro sampling method" with focused ion beam was applied to fabricate the specimen from the interested region in a shorter term. In growing oxide materials on Si substrate, a proper termination was found to be inevitable for avoiding surface oxidation. Arsenic was used to obtain a durable surface of Si in oxygen atmosphere. CeO2 and SrTiO3 were tried to grow and the interfaces were characterized using these method.
Combinatorial chemistry has been developed as an experimental method where it is possible to synthesize hundreds of samples all at once and examine their properties. Recently, we introduced the concept of combinatorial approach to computational chemistry for material design and proposed a new method called `a combinatorial computational chemistry'. In this approach, the effects of large number of dopants, substrates, and buffer layers on the structures, electronic states, and properties of metal oxide electronics material is estimated systematically using computer simulations techniques, in order to predict the best dopant, substrate, and buffer layer for each metal oxide electronics materials.
We present the observation results of a single string DNA (deoxy ribo nucleic acid) obtained by collection mode near- field optical microscopy operated under constant distance mode with the optical near field intensity as the feedback signal. The observed width of the narrowest string is 4 nm. To our knowledge, this is not only the successful optical observation of a single string DNA by purely optical means but also under such high resolving capability. These are attributed to the special care taken during the sample preparation to avoid unwanted scattered light and to the probe which were specially designed to enhance the local near field interaction. All these factors make the probe picks up efficiently the high spatial frequency components of the scattered near field at the same time rejecting effectively the lower spatial frequency components.
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