Protein (bovine serum albumin; BSA)-drug (indomethacin; IM) nanocomposites were prepared by pulsed laser deposition (PLD) at two wavelengths, infrared (1064nm) and ultraviolet (266nm), from uniformly dispersed mixture of BSA and IM as a target. Composite particulates under 50nm were obtained with the coexistence of larger agglomerates over 200nm. Primary structure of BSA is preserved after laser irradiation by both wavelengths. Effects of electronic and vibrational excitation by UV and IR laser respectively on the secondary structure of the nanocomposites were examined by Fourier transform infrared spectroscopy (FT-IR). Chemical shift towards lower wavenumber and a broadening of the amide I band due to PLD treatment were observed by FT-IR. From curve fitting of the amide I into five components, we found the decrease in the ratio of α-helical / β-sheet components with increasing the laser fluence. The secondary structure of BSA is more sensitive to the laser fluence than the wavelength.

Sputter rippling refers to the formation of regular surface patterns during glancing incidence energetic ion beam etching of surfaces, usually as a result of a competition between etching (from the ion beam) and capillary action (driving smoothening via surface diffusion). Many different kinds of morphologies are often observed, including ripples oriented parallel and perpendicular to the projected ion beam direction and “quantum dots” arranged in hexagonal or rectangular arrays. Theoretical analyses of ripple evolution have concentrated on the initial stages of the surface instability leading to pattern formation, and the details associated with the nonlinear mechanisms leading to amplitude saturation and pattern stabilization remain a subject of active interest. The Si(111) surface is a single component surface with isotropic surface diffusion kinetics; for these reasons, this system provides a useful probe of surface evolution without complicating effects of compositional inhomogeneities and anisotropic terrace diffusion. Our examination of the Si(111) surface indicates that step-step interactions may play an important role in the evolution of sputter ripples in this system. To argue for this conclusion, a comparison with sputter ripple evolution on Si(001) is made.

CaF2 is widely adopted as deep-UV window material and thin film optical coating. It has been known that ordered defect superlattices may form in electron irradiated CaF2.[1] However, the nature of the defects on the superlattice point (i.e., Ca colloids or voids) has not been certain and the self-organization mechanism has not been fully understood. In this study, single crystal CaF2 were irradiated under 200 keV electron beam at room temperature with in situ TEM observation of the dynamic process of defect ordering. The superlattice reached steady state after an electron dose of 1×1021e-/cm2 with void radius about 5 nm. Videos recorded during the in-situ observation reveal the dynamic self-organization process of the void superlattice. Coalescence was prevalent at the initial stages. Migration and preferential growth were dominant at the final stages of the superlattice formation. At a dose higher than 3×1021 e-/cm2 the superlattice structure was destroyed. These critical doses of void superlattice formation and deformation seem to be independent of dose rate. The anisotropic diffusivity of the migrating “molecules” may explain the superlattice formation.

We developed a method to fabricate nanoscale pits having high aspect ratio, using a scanning tunneling microscope with an attached carbon nanotube (CNT) probe. CNT probes used in this study were synthesized by the pulling method. The nanostructures were produced in Au thin film in an ambient pressure and room temperature. The results of our experiment show that a threshold value exists for the fabrication of the pits between 1 V and 2 V. The depth and diameter of the pit increased with the increase in the bias voltage and tunnel current, respectively. Consequently, a bias voltage of 3 V and tunnel current of 4 nA were found to be the optimum conditions for a high aspect ratio nanoscale pit fabrication. In changing the fabrication time at the optimum conditions, the depth of the pit increased with the increase in the fabrication time, with little change in the diameter of the pit. This demonstrates that CNT probes can be useful for fabricating nanoscale structures.

A new template method for large-scale fabrication of hexagonally patterned and vertically aligned ZnO nanowires is demonstrated. The process involves a novel type of metal membrane, a gold catalyst template produced using the membrane as deposition mask, and the catalyst-guided growth of ZnO nanowires. The metal membranes, composed of hexagonal nanohole arrays, are electrochemically replicated from ordered porous alumina. The ZnO nanowires obtained have a uniform alignment perpendicular to the GaN surface and a distribution according to the pattern defined by the nanohole membrane. Such periodically arranged ZnO nanowires have potential applications as sensor arrays and piezoelectric transducers.

Mesa structures fabricated on Si(111) surfaces have been found experimentally to develop step arrays with large spacing of the order of a micron or more after annealing at temperatures where sublimation becomes important. Ridges around the edges initially develop during annealing and form barriers to step motion before eventually breaking down. This produces an array of steps of the same sign with a few wide terraces. Computer simulations using one dimensional Burton, Cabrera and Frank (BCF) theory including attachment-detachment rates and step-step repulsion for this configuration show that the terraces evolve under different dynamics depending on the terrace widths. For large terrace widths, sublimation dominates the step dynamics and the Ehrlich-Schwoebel effect is negligible. Sinusoidal terrace width distributions result in this case. The experimentally measured step distribution has such a sinusoidal shape suggesting that the step dynamics is sublimation dominated on the mesas after ridge breakdown.

We have investigated the initial stage of the growth of obliquely deposited Fe on a Si substrate held at 470 °C with atomic force microscopy (AFM) and high resolution Rutherford backscattering spectroscopy (HRBS). During the deposition from the normal direction, many Si atoms are displaced from their lattice position due to the reaction with the deposited Fe. On the contrary, the number of displaced Si atoms decreases significantly, and the nanoislands of a few 10 nm in diameter grow selectively when Fe is deposited at 85°. This is clear evidence that the local nucleation processes for the Fe silicide formation is modified by the geometrical deposition conditions.

Atomically flat surfaces can be obtained by high-temperature annealing in UHV of specially patterned silicon samples. Thin silicon oxide layers were grown by dry oxidation on three types of surfaces: (a) atomically flat surfaces, (b) normal (stepped) surfaces cleaned in UHV by the same high-temperature annealing and (c) normal wafer surfaces, which underwent just an RCA chemical cleaning before oxidation. Atomic force microscopy (AFM) was performed to reveal the topography of the surfaces. Aluminum pads were deposited on these oxidized surfaces using photolithography techniques. The leakage current through the oxide was measured for all three cases. Our results show that the smoother the surface before oxidation, the smaller the leakage current.

A new nanowire growth technique using annealing and pulsed laser deposition is described. The technique demonstrates the control in the precise nanowire growth temperature thereby yielding higher quality nanowires than obtained from simple annealing alone. InSb substrate and gold target were used to demonstrate the new technique. The results from the variation of gold deposits from 2.5 mins to 40 mins at the fixed growth temperature of 510 °C are discussed.

The evolution of ion beam eroded Silicon surfaces was measured in real-time by combining focused ion beam technology with scanning electron microscopy. By detecting the secondary electrons emitted during implantation the surface was monitored in-situ during the erosion process of a Gallium focused ion beam. Repetitive scanning of the ion beam over the surface effectuates a coherent erosion of the exposed surface area, with the continuum theory of erosion as the ergodic limitation. Surface ripple as proposed by linear erosion theory were observed for oblique incidence of the ion beam and their propagation with progressing erosion time as well as their velocity dispersion were monitored. The ripple wavelength has been observed to increase with the erosion time and the value of the ripple velocity was observed to agree qualitatively with the results of Monte-Carlo simulations of the erosion process.

Noise effects acompanying the erosion process are found to be responsible for the reorientation of the ripples when the orientation of the ion beam onto the surface is varied. This mechanism is discussed to stimulate further efforts in this field of surface erosion.

The effect of atomic hydrogen on the growth mode and surface morphology of GaAs(110) thin films grown by molecular beam epitaxy (H-MBE) has been studied for different kinetic regimes using atomic force microscopy (AFM). Growth in the Ga supply-limited regime after H-assisted oxide removal leads to the formation of multi-atomic step arrays by step bunching with a very uniform terrace size distribution in the 80 nm range. Growth under As-deficient conditions after H-assisted oxide removal induces a rapid self-organization of the GaAs(110) surface into a ridge pattern along the <001> tilt direction, which is broken down into a 3D mound morphology when H is also present during growth. A chacteristic nanofacetting of the surface with very straight <1–10> -type steps is observed at high temperatures regardless of atomic hydrogen being used during oxide desorption and/or epitaxial growth.

In this study, we explored the possibility of using annealed non-continuous metal film enabled etching technique to produce large nano-structured surfaces. Non-continuous Ag film is deposited on silicon wafer with a thin layer of silicon dioxide using E-beam deposition, and then vacuum thermal annealing was applied on the deposited films, causing nano-scaled Ag particles to migrate and agglomerate into self-assembled islands of larger nanometer dimensions. We controlled the density and average size of the metal islands through thickness of the initial film and subsequent annealing rates. Reactive ion etching through the metal islands mask into the underneath silicon dioxide layer was performed following the annealing process. Preliminary hydrophobicity experiments were carried out using the engineered nano-structured surfaces.

At present, there is a consensus that various Stress Driven Rearrangement Instabilities (SDRI) are the implications of the mathematically rigorous theoretical Gibbs thermodynamics. Many applied researchers and practitioners believe that SDRI are also universal physical phenomena occurring over a large range of length scales and applied topics. There is a multitude of publications claiming experimental observation of the SDRI based phenomena. This opinion is challenged by other highly respected scholars claiming theoretical inconsistencies and multiple experimental counterexamples. Such an uncertainty is too costly for further progress on the SDRI topic. The ultimate goal of our project is to resolve this controversy.

The project includes experimental, theoretical, and numerical studies. Among various plausible manifestations of SDRI, the authors focused only on two most promising for which the validity of the SDRI has already been claimed by other researchers: a) stress driven corrugations of the solid-melt phase interface in macroscopic quantum 4He and b) the dislocation-free Stranski-Krastanov pattern of growth of semiconductor quantum dots. We devised a program and experimental set-ups for testing applicability of the SDRI mechanisms using the same physical systems as before but using implications of the SDRI theory for 2D patterning which have never been tested in the past.