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We report a gold substrate manipulation from very-flat to highly-curved surfaces with a thermal treatment as a function of annealing temperature, which greatly affects the quality of SAM with respect to density and ordering. Annealing of gold film greatly removes nanometer-scale protrusions, leading to a very-flat surface with a large grain size as comparable with gold coating on mica. The quality of alkanethiol SAM are evaluated using Fourier transform infrared and time of flight secondary ion mass spectroscopy. Our proposed method delivers good ordering between molecules in the SAMs to promote a high density on extremely small areas for a cost-effective and miniaturized biochip.

We have investigated the optimal growth conditions of carbon nanotubes (CNTs) using the chemical vapor deposition and the Ni nanoparticle arrays. The diameter of the CNT is shown to be controlled down to below 20 ㎚ by changing the size of Ni particle. The position and size of Ni particles are controlled continuously by using wafer-scale compatible methods such as lithography, ion-milling, and chemical etching. Using optimal growth conditions of temperature, carbon feedstock, and carrier gases, we have demonstrated that an individual CNT can be grown from each Ni nanoparticle with almost 100% probability over wide area of SiO₂/Si wafer. The position, diameter, and wall thickness of the CNT are shown to be controlled by adjusting the growth conditions.

Thin ZnS 0.78 Te 0.22 layers embedded in ZnTe matrix have been grown on GaAs (1 0 0) substrate by hot-wall epitaxy technique with varying growth time. Their optical properties have been investigated by photoluminescence (PL) measurements at low temperature and by temperature-dependent PL measurements. PL measurements show that the quantum dots (QDs) related peak at lower energy side with a broad full-widths at half-maximum (FWHM) and the two-dimensional (2D) layer related peak at higher energy side with a narrow FWHM are clearly resolved and their energies shift to lower energies as the ZnS 0.78 Te 0.22 growth time increases. It is also found from temperature-dependent PL measurements that the activation energy of QDs is almost two times larger than that of 2D layer. Atomic force microscopy confirms their quantum dot formation.

We report dielectric function spectra of disordered GaAs1−xPx alloys measured using spectroscopic ellipsometry at room temperature in the 1.5–5.5 eV photon energy region. Energies of the interband-transition edges, E0, E1, E0′, and E2, of the alloys were determined by line-shape analyses on their dielectric functions. It is found that the E1, E0′, and E2 energies of the alloys increase linearly with the increase of the P composition between those of GaAs and GaP while the increase of their E0 energy shows finite positive bowing. The energy separation between the E1 and its spin-orbit-split E1+Δ1 edges of the alloys decreases linearly with the increase of the P composition with their lifetime broadenings becoming larger than those of the binary compounds by more than 20%. The effect of compositional disorder on the electronic structure of GaAs1−xPx alloy system was discussed based on the present optical data.

Variation of dielectric response function of Si 0.8 Ge 0.2 Si (001) epitaxial films for varying layer thickness was detected by spectroscopic ellipsometry measurements. As the epilayer thickness increases, interband-transition structures near 3.3 eV by E′0, E1 and E1 + Δ1 edges and near 4.2 eV by E2 edges of Si0.8Ge0.2 are found to shift gradually to lower energies indicating gradual relaxation of lattice-mismatch-induced strain in the epilayer. Result of a line-shape analysis on the dielectric functions of the alloys indicates that the rates of the strain-induced energy shifts of the E1 and E1 + Δ1 edges are larger than those of the E′0 and E2 and also the energy splitting between the E1 and E1 + Δ1 increases as the strain in the film increases. The strain dependence of the E1 and E1 + Δ1 energies of the alloys agrees fairly with the result of a theoretical estimation based on the deformation potential theory.

Optical properties of zine-blende Zn 1− x Mg x Se ( x ≤ 0.21) alloys grown epitaxially on GaAs(0 0 1) by molecular beam epitaxy have been studied using spectroscopic ellipsometry at room temperature in the 1.5–5.5 eV photon energy region. Using the measured dielectric functions and their second-derivative spectra, the energies of the interband critical-point edges, E 0 , E 1 and their spin-orbit splittings, have been determined. These edges are found to shift linearly to higher energies as the Mg composition increases. The rates of increase of the E 0 and E 1 edges of the alloys are 10 and 4.7 meV/at.% respectively and their spin-orbit splittings remain at about the same as those of ZnSe. The increase rate of the E 0 edge of the present zinc-blende alloys is found to be smaller by about 20% than that of Bridgman-grown bulk sphalerite alloys [ J. Crystal Growth , 159 , 1996, 167].

Optical properties of dilute Fe1−xSix (x⩽0.1) alloys were studied by spectroscopic ellipsometry in the 1.5–6 eV photon energy region. The absorption strength of the alloys is found to decrease in the entire energy region as the Si composition increases. The interband-transition edges of Fe at about 2.5 eV in the minority-spin bands and at about 5 eV in the majority-spin bands shift to lower energies as the Si composition increases. The decrease in the absorption strength is interpreted as due to a decrease in the density of states of the Fe host and also due to a reduction of conduction-electron concentration in the alloys. The shifts of the 2.5 and 5 eV interband-transition edges can be explained in terms of a perturbative variation in the band structure of Fe induced by its alloying with Si.

Optical properties of ZnS0.78Te0.22/ZnTe single quantum wells grown on GaAs (100) substrates by hot wall epitaxy technique with varying the ZnS0.78Te0.22 well width from 0.3 to 1.8 nm were investigated by photoluminescence (PL) measurements at low temperature and by temperature-dependent PL measurements. PL results show the evidence of type-II transition and their peak energy shifts to higher energies as the ZnS0.78Te0.22 well width decreases. In addition, temperature-dependent PL measurements show the increase of the activation energy as the well thickness decreases, indicating the increase of confinement effect. This study makes it possible to introduce proper band diagram for this structure, and can give very useful information on their device applications.

Optical properties of SrBi2Ta2O9 (SBT) ferroelectric thin films were investigated by spectroscopic ellipsometry at room temperature in the 1.5–5.5 eV spectral range. The films were grown on platinized silicon (Pt/Ti/SiO2/Si) with a Bi/Sr ratio (x) range from 1.2 to 2.8 by pulsed-laser deposition. The measured pseudodielectric functions of the samples indicate the band-gap energy of SBT shifts to lower energies as x increases. The optical constants and band-gap energies of the SBT films were determined through multilayer analyses on their pseudodielectric functions. The band-gap energy of SBT is found to shift to lower energies quite linearly with x. The band-gap energy at stoichiometric composition (x=2) is estimated to be 4.1 eV.

We fabricated quantum dot arrays using anodic alumina mask. We grew an alumina template on Si wafers by two-step anodization. The porous alumina template thus grown is used as a mask for metal deposition. After thermal evaporation and removal of the mask, we fabricated the quantum dot arrarys on a Si substrate. Using this template-assisted method we obtained a high density array of quantum dots in a large scale. These quantum dots have a narrow size distribution which can be easily controlled by a pore widening of templates from 20 to 60 nm.

We report resistive switching characteristics of single-crystalline Ni/NiO core/shell nanodisk arrays, in which the conducting filaments are highly localized on the surface of nanostructure. The local current distributions observed in such a single-grained nanodisk demonstrate that the contact area and the contact time between the conductive tip of conducting atomic force microscopy and the surface of nanodisk critically influence the voltage-stress-induced electroforming behaviors of nanofilaments in NiO switching nanoblocks. These contact parameters, such as the contact area and the contact time, are interpreted to the electrode size and the voltage-stress time for the formation of filaments in metal oxides.

A simple procedure for the fabrication of sub-10 nm scale Si nanopillars in a 2-D array using reactive ion etching with 8 nm Co nanoparticles as etch masks is demonstrated. The obtained Si nanopillars are single crystalline tapered pillar structures of 5 nm (top) x 8 nm (bottom) with a density of approximately 4 x 10(10) pillars cm(-2) on the substrate, similar to the density of Co nanoparticles distributed before the ion etching process. The uniform spatial distribution of the Si nanopillars can also be patterned into desired positions. Our fabrication method is straightforward and requires mild process conditions, which can be extended to patterned 2-D arrays of various Si nanostructures.