We report the growth of Si nanostructures, either as thin films or nanoparticles, on graphene substrates. The Si nanostructures are shown to be single crystalline, air stable and oxidation resistive, as indicated by the observation of a single crystalline Si Raman mode at around 520 cm –1 , a STM image of an ordered surface structure under ambient condition, and a Schottky junction with graphite. Ultra-thin silicon regions exhibit silicene-like behavior, including a Raman mode at around 550 cm –1 , a triangular lattice structure in STM that has distinctly different lattice spacing from that of either graphene or thicker Si, and metallic conductivity of up to 500 times higher than that of graphite. This work suggests a bottom-up approach to forming a Si nanostructure array on a large-scale patterned graphene substrate that can be used to fabricate nanoscale Si electronic devices.

The PN junction was introduced in transistors by doping, resulting in high losses due to Coulomb scattering from the dopants. The MOSFET introduced carriers in the form of electrons and holes with an applied bias to the oxide barrier, resulting in carrier transfer without doping. This avoids high scattering losses and dominates the IC industries. With heterojunctions having valence-band maxima near and even above the conduction-band minimum in the formation of Type-III superlattices, very useful devices, introduced by Tsu, Sai-Halacz, and Esaki, soon followed. If the layer thicknesses are more than the carrier mean-free-path, incoherent scattering results in the formation of carrier transfer via diffusion instead of opening up new energy gaps. The exploitation of carriers without scattering represents a new and significant opportunity in what we call a Broken Gap Heterojunction FET.

We report the growth of Si nanostructures, either as thin films or nanoparticles, on graphene substrates. The Si nanostructures are shown to be single crystalline, air stable and oxidation resistive, as indicated by the observation of a single crystalline Si Raman mode at around 520 cm-1, a STM image of an ordered surface structure under ambient condition, and a Schottky junction with graphite. Ultra-thin silicon regions exhibit silicene-like behavior, including a Raman mode at around 550 cm-1, a triangular lattice structure in STM that has distinctly different lattice spacing from that of either graphene or thicker Si, and metallic conductivity of up to 500 times higher than that of graphite. This work suggests a bottom-up approach to forming a Si nanostructure array on a large scale patterned graphene substrate for fabricating nanoscale Si electronic devices.

In this study we report thermal evaporation technique as a simple method for the growth of 4H silicon carbide on p-type silicon substrate. A mixture of Si and C60 powder of high purity (99.99%) was evaporated from molybdenum boat. The as grown film was characterized by XRD, FTIR, UV-Vis Spectrophotometer and Hall Measurements. The XRD pattern displayed four peaks at 2Θ angles 28.550, 32.700, 36.100 and 58.900 related to Si (1 1 1), 4H-SiC (1 0 0), 4H-SiC (1 1 1) and 4H-SiC (2 2 2), respectively. FTIR, UV-Vis spectrophotometer and electrical properties further strengthened the 4H-SiC growth.

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In this study, the analysis of HRTEM images of SiC on p-type Si (111) deposited by MBE was performed. Fullerene C60 and Si are used in growth process as solid sources. Carbonization of substrate is done at temperature 600 oC before starting the growth of SiC to reduce lattice mismatch. During 4 hour growth process the temperature of substrate and C60 was 1100 0C and 625 0C respectively and chamber pressure was 1.4×10-9 Torr. The sample was characterized using HRTEM and EDAX. Surface analysis shows that the grown film contains vacancies, voids, stacking faults of intrinsic nature, and twinning along (111) plane. The change in structure from stable 3C-SiC to 6H-SiC has been observed.

A drop of phosphorus 'spin on dopant 430' was sprayed on ZnO pellets (prepared from 99.9999% ZnO powder) and sintered in air in the temperature range of 500 to 1000 degrees C with a step of 100 degrees C for one hour in a programmable diffusion furnace. Characterization of as-prepared ZnO pellets was performed by various diagnostic techniques: e.g., X-ray diffraction confirmed hexagonal structure of ZnO pellets preferably along (002) direction. We observed forward shift in 2 theta value of the X-ray diffraction pattern of ZnO sintered at temperature 1000 degrees C. We correlate the forward shift with the involvement of phosphorus with vacancy at Zn site. Theoretical calculations on a 32-atoms super cell of phosphorus doped ZnO further supported the argument in the shape of a shallow acceptor P-Zn - 2V(Zn) complex on Zn site. Typical PL spectra displayed band-to-band transitions peak and an additional donor-acceptor peak at similar to 3.14 eV in all samples

The de Broglie relation is a consequence of Planck-Einstein's energy quantization plus Lorentz invariance in describing any system of interaction. Once interaction results in a stable minimum energy configuration, the system, including low dimensional structures and devices, transforms into a particle, without further interactions. However any attempt to make observation of the particle, the interaction causes the entity to revert back to the realm of quantum mechanics. Certain steps may be described by the use of constitutive equations obtained by the use of RPA, Random Phase Approximation, resembling classical descriptions such as refractive index, deformation potentials, effective mass and others. All interactions are quantum mechanical, even appear to be classical.

3C-SiC thin films have been grown by Molecular Beam Epitaxial (MBE) technique on a Si (111) substrate at 1050 degrees C using a single solid source fullerene (C60). Fullerene molecules adsorb on the tissue like surface of substrate and then thermally decompose into amorphous carbon and produce 3C-SiC. The grown films were characterized by SEM/EDX, XRD, FTIR and Raman spectroscopy. XRD data confirmed the growth of thick, highly crystalline and epitaxial SiC. The grown film has amorphous surface but the inner core consists of nearly perfect crystalline lattice structure indicated by SEM. FTIR and Micro-Raman also confirmed the high crystalline growth of 3C-SiC. The method proves to be a milestone for low temperature and high crystalline growth of 3C-SiC.

We report deep level transient spectroscopy results from ZnO layers grown on silicon by molecular beam epitaxy (MBE). The hot probe measurements reveal mixed conductivity in the as-grown ZnO layers, and the current-voltage (I-V) measurements demonstrate a good quality p-type Schottky device. A new deep acceptor level is observed in the ZnO layer having activation energy of 0.49 +/- 0.03 eV and capture cross-section of 8.57 +/- 10(-18) cm(2). Based on the results from Raman spectroscopy, photoluminescence, and secondary ion mass spectroscopy (SIMS) of the ZnO layer, the observed acceptor trap level is tentatively attributed to a nitrogen-zinc vacancy complex in ZnO.

Theoretical evidence of V-O-Zn-i to be a native donor in bulk ZnO has been under debate. To resolve the issue, we annealed several pieces of as grown zinc rich n-type ZnO thin film having N-D similar to 3.26 x 10(17) cm(-3) grown by molecular beam epitaxy on Si (001) substrate in oxygen environment at 500 degrees C - 800 degrees C, keeping a step of 100 degrees C for one hour, each. Room temperature Hall measurements demonstrated that free donor concentration decreased exponentially and Arrhenius plot yielded activation energy to be 1.2 +/- 0.02 eV. This value is in an agreement with the theoretically reported activation energy of V-O-Zn-i donor complex in ZnO.

Recent progress in the area of hyperbolic metamaterials (HMMs) has sparked interest in transparent conducting oxides (TCOs) that behave as plasmonic media in the near-IR and at optical frequencies for imaging and sensing applications. It has been shown that by depositing alternating layers of negative-epsilon/positive-epsilon materials, a medium can be created with unusual index values such as near zero. HMMs support high-k waves corresponding to a diverging photonic density of states (PDOS), the quantity determining phenomena such as spontaneous and thermal emission. Also, modeling such structures allows evanescent fields containing sub-wavelength information to be coupled to propagating radiation. We investigate the optical, electronic, and physical properties of radio frequency plasma-assisted molecular beam epitaxial (RF-MBE) growth of alternating layers of ZnO and TCO of uniform thickness for HMM applications. Preliminary work creating HMMs with ZnO and Al-doped ZnO (AZO) has shown a negative real part of the permittivity at near-IR whose modulus is proportional to the number density of Al dopant. However, increasing the Al content of the AZO increases the transmission losses to unacceptable levels for device applications at industry standard wavelengths. A TCO with conductivity and physical structure superior to that of AZO is gallium-doped ZnO (GZO). Uniformly grown GZO has been demonstrated to possess improved crystal quality over AZO due to the higher diffusivity of Al in the ZnO. AZO and GZO HMM structures grown by RF-MBE are characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), Hall effect, four-point probing, deep-level transient spectroscopy (DLTS), ellipsometry, visible and ultraviolet spectroscopy (UV-VIS) and in-situ reflection high energy electron diffraction (RHEED).

Physics is built on the use of constitutive equations governed by the Random Phase Approximation to deal with cancellations resulting from space-time variations of the phase of waves. Special handling of phase becomes possible in engineered materials, such as domain formations and periodicity. When dealing with interactions involving superlattices as well as metamaterials, the phase of electron or electromagnetic waves can be exploited in numerous ways. Examples include systems with gain such as amplifiers and oscillators, as well as serving as passive impedance matching elements such as image formation with lenses.

The Gd2O3 layer grown by electron beam evaporation system normally leads to oxygen deficient sites unless the oxygen partial pressure is provided. These oxygen vacancies were monitored through their current modulating effect. This modulation controlled the current within a Si well of the Gd2O3/Si/Gd2O3 quantum well structure through the migration of the oxygen vacancies. Such behavior were not found in the structure that contains far less oxygen vacancy such as SiO2/Si/SiO2 structure.

Diamond crystallites were found on titanium/sapphire surface as a result of evaporation of C-60 from effusion cell in molecular beam epitaxy (MBE) reactor. Substrate temperature, effusion cell temperature and base pressure of the MBE chamber were set as 1050 degrees C, 650 degrees C and 1 x 10(-9) Torr, respectively. Raman scattering of the as-grown layers revealed the existence of diamond and graphite at 1337 cm(-1) and 1592 cm(-1), respectively. Moreover, x-ray-diffraction pattern, micrographs exposed from scanning electron microscopy and optical microscopy also confirmed the evidence of MBE diamond crystallites.

The story leading to the successful introduction of the GaAs/GaAlAs man-made superlattice is probably not known to most. Before I joined IBM and started working under Leo Esaki, I was working and teaching in Texas after I left Bell Labs. My boss, the head of Physics Research at Southwest Research Institute, Frank Witmore, showed me a new book: The Dynamics of Conduction Electrons by A.B. Pippard, Blackie & Son Limited, 1964. He discussed what happens to metals if the mean free path is sufficiently long. For example, electrons move toward the Brillouin zone boundary under the application of an electric field, and are reflected resulting in oscillations.

While artificial or man-made structures date back to Lord Rayleigh, the work started by Lewin in 1947, placing spheres onto cubic lattices, greatly enriched microwave materials and devices. It was very suggestive of both metamaterials and photonics crystals. Effective medium models were used to describe bulk properties with some success. The concept of metamaterials followed photonic crystals, and these both were introduced after the introduction of the man-made superlattices designed to enrich the class of materials for electronic devices. The work on serrated ridged waveguides by Kirschbaum and Tsu for the control of the refractive index of microwave lenses as well as microwave matching devices in 1959 used a combination of theory, such as Floquet's theory, Bloch theory in one dimension, as well as periodic lumped loading. There is much in common between metamaterials and superlattices, but in this paper, we discuss some practical limitations to both. It is pointed out that unlike superlattices where kl > 1 is the most important criterion, metamaterials try to avoid involve such restrictions. However, the natural random fluctuations that limit the properties of naturally occurring materials are shown to take a toll on the theoretical predictions of metamaterials. The question is how great that toll, i.e. how significant those fluctuations will be, in diminishing the unusual properties that metamaterials can exhibit.