Composites of single wall carbon nanotubes (SWNT) and conductive polymers were studied as potential cathode materials for application in polymer light emitting devices. A new conductive poly(2,7–9,9 (di(oxy-2,5,8-trioxadecane))fluorene) (PFO) possessing surfactant properties was used to stabilize SWNTs in solutions. The rigid PFO backbones act as a template while the ethyleneoxide side chains appear to wrap around the SWNTs. Up to 0.02% (by weight) of SWNTs are stabilized in the solution phase. The current vs. voltage behavior of the SWNT/PFO composite film (2% SWNT in PFO by weight) shows that most of the current is carried by SWNTs.

Fluorocarbon was photo-chemically combined to a fused silica glass with the silicon oil used as a bonding agent. Balsam, unsaturated polyester resins and UV hardening adhesives have been generally used for joining two optical glasses together. They, however, have a strong absorption band in the UV region. Therefore, a new bonding method was developed for optical materials to allow UV rays to pass through using silicone oil and excimer- lamp. This new method requires the fluorocarbon-polishing pad employed in our PCP (Photo-Chemical Polishing) method in hydrofluoric acid ambience, which is bonded with the silica glass. The silicone oil was put between the fused silica glass and the fluorocarbon (FEP), and an excimer- lamp was irradiated. When the excimer lamplight was irradiated vertically, the silicon oil ((-O-Si(CH3)-O-)n) was photo-dissociated and reacted with the oxygen adsorbed on the silica glass surface to produce a SiO2. On the other hand, the H atoms photo-dissociated from the silicon oil pulled out the F atoms of the FEP. As a result, the FEP and the silica glass were combined. The tensile strength of the sample bonded by the photo-chemical reaction was evaluated. The tensile strength of 5.4 [kgf/cm2] was obtained, whereas that of the non-treatment sample was nil. Moreover, the transmittance of the vitrified silicone oil was measured at the 193 nm of ArF laser wavelength. It increased by 90.6% from 29.2% without the UV photon irradiation. The results showed that the silicon oil changed to silica glass by the excited oxygen, which improved the UV rays under 200nm transmittance.

The surface electronic properties of the nitric oxide (NO) treated indium tin oxide (ITO) are examined in-situ by a four-point probe and X-ray photoelectron spectroscopy (XPS). The XPS N1s peak emerged at a high binding energy of 404 eV indicating that NO is reactive with ITO. NO adsorption induces an increase of film sheet resistance, arising from an oxygen rich layer near the ITO surface region, with approximately 2.5 nm thick. This implies that the interaction of NO with ITO is occurred around surface region. Valence band maximum measured for NO-absorbed ITO was shifted to the low binding energy side. This is related to the upward surface band bending.

The structural and electrical properties of boron doped amorphous silicon-germanium alloy films, obtained using a low frequency plasma enhanced chemical vapor deposition (LF PECVD), are presented in this contribution. These thin films were deposited on a substrate heated at 270°C, and by decomposing a mixture of silane, germane, and diborane gases. The chemical bond structure was studied by Infrared Spectroscopy. Our results show that, for a constant diborane flow, the increase of germane flow enhances the incorporation of boron into the film; the peak at 2540 cm−1 becomes larger as the Ge content increases. Transport of carriers was studied by measuring current-voltage curves as a function of temperature. The conductivity increased from 10−6 to 10 (Ω-cm)−1, while the refraction index increased from 3.312 to 4.4458, for an increasing Ge content; this makes the films suitable for optical waveguide applications. On the other hand, the activation energy varied from 0.668 to 0.220 eV when the sample was doped with boron. The AFM images showed that the surface roughness was improved for an alloy with 50% of Ge.

We review distinct photonic/electronic properties onginating from built-in nano-structures in transparent oxide based matenals, emphasizing potential of nanostructures hidden in crystal structure. Matenals focused are oxychalcogenides LaCuOCh (Ch=chalcogen ion) and homologous oxides InGaO3(ZnO)m(m=integer) having naturally formed multi-quantum well structures. Novel functions and devices ansing from the built-in nanostructure are: (1) modulation doping of positive holes and room temperature stable exciton in LaCuOCh, (2) high performance transparent field-effect transistor fabncated in InGaO3(ZnO)5 epitaxial thin films, and (3) conversion of insulator to persistent electronic conductor by carner doping in 12CaO 7A12O3 (C12A7).

Transparent electronics is an embryonic technology whose objective is the realization of invisible electronic circuits. We have recently reported the fabrication of a novel n-channel transparent thin-film transistor (TTFT). [1] This ZnO-based TTFT is highly transparent and exhibits electrical characteristics that appear to be suitable for implementation as a transparent select-transistor in each pixel of an active-matrix liquid-crystal display. Moreover, the processing technology used to fabricate this device is relatively simple and appears to be compatible with inexpensive glass substrate technology. The objective of the work reported herein is to summarize some of our recent TTFT electrical performance results. Materials, processing, and device structure details related to these devices appear in future publications.

Photoelectric properties have been investigated for the organic dye thin film cells utilizing surface plasmon (SP) excitation. The cells fabricated in this work had a prism/Al thin film/copper phtalocyanine (CuPc) thin film/Ag thin film structure, which was the Kretschmann configuration in the attenuated total reflection (ATR) method. Since the CuPc thin film exhibits p-type conduction, the Schottky and Ohmic contacts can be obtained at the interfaces between the CuPc and Al thin films and between the CuPc and Ag thin films, respectively, and the cells used in this work show photoelectric properties. The ATR and short-circuit photocurrent properties have been simultaneously measured as a function of the incident angles of the laser beams. The experimental and calculated results of the ATR and short-circuit photocurrent properties and the optical absorptions of the organic dye layers were discussed. It was found that the photoelectric effect in the organic dye thin film cells the Kretschmann configuration in the ATR method was enhanced by the SP excitation.

Direct conversion of sunlight into electricity employing amorphous (a-Si:H) and microcrystalline (mc-Si) silicon solar cell structures provides cheap, continuous, large-area device capability. However, the inherent instability due to light induced degradation of such cells poses a challenge for practical photovoltaic applications. To work around this problem, we have made use of a-Si:H/c-Si (crystalline) and mc-Si/c-Si heterostructures. Plasma decomposition of 2% silane gas (SiH4/He) in an ECR (electron cyclotron resonance)-CVD configuration forms the basis of the deposition technique. Electro-optical properties exhibit photoconductivity (σp) of 6.5×10−6 S/cm and a low dark conductivity (σd) of 1.4×10−9 S/cm for a-Si:H films and a relatively high σp of 2.1×10−4 S/cm and a high σd of 1.2×10−7 S/cm for mc-Si films. A possible multi-tunneling transport mechanism is evident for a low forward bias with the current conduction becoming space charge limited with increasing bias. The domination of this latter mechanism may be responsible for non-ideal junction behavior.

The CuInGaSSe2/CdS heterostructure interface has a special effect on the performance of an important thin film photovoltaic device. The CdS buffer layer is essential to stabilize the performance of CuInGaSSe2 based devices. It adjusts the lattice mismatch at the absorber/window interface, repairs CuInGaSSe2 surface defects and protects it from air oxidation. Unfortunately, the CdS material has many environmental issues. This paper reports an alternate chemical approach to engineer the interface defects in CuInGaSSe2 and maximize its PV output. It describes a simple processing step to manipulate the defect density. This step could potentially reduce sensitivity to the ambience, widen the surface bandgap and replace the current hazardous processes used in state-of-the-art CuInGaSSe2 modules. Photocurrent and spectral response measurement in an electrolytic medium monitor the effects of surface modification, specific metal ions and time. The CuInGaSSe2 films respond easily to a number of external stimuli with either positive or negative changes in the electro-optic properties. Strong time dependence of the photocurrent suggests a dynamic equilibrium of point defects in the CuInGaSSe2 film. The results provide new insights into the effects of stoichiometry, deposition methods and oxide formation, on the defect chemistry. They also provide directions for reconfiguring the deep defects for enhanced device performance without the need for toxic etchants or buffer layers, and the environmental hazards associated with these steps.

Thin-film devices pose unique challenges to device simulators. Relaxation approximations to the Boltzmann Transport Equation may be vitiated as the width and length of the thin-film components approach the mean free path lengths of electrons and phonons. Concomitant with these reduced lengths, surface and other interface scattering mechanisms exert greater influences on the transport processes. Consequently, it may not be effective to use transport models that depend upon analytic or other pre-ordained representations of electron, phonon, and photon distribution functions. Finally, thin-film simulations must account for tunneling processes, local defects, nanoscale dopant gradients, nanoscale roughness, and nanoscale variations in local geometries. Consequently, it is desirable to develop a nanoscale simulation technique that (1) can arbitrarily vary material properties in real space while (2) tracking reciprocal space scattering for arbitrary and volatile distributions of electrons, phonons, and photons. The Discrete State Simulation (DSS) forms the backbone of such a simulation. Written with the run-time flexibility of object-oriented code, the Discrete State Simulation (DSS) is a coupled cellular automata (CA) simulator that builds upon the objects and rules of quantum mechanics. The DSS represents global non-equilibrium processes as patterns that emerge through an ensemble of scattering events that are localized at vibronic nodes. The run-time flexibility of the DSS enables dynamic rule construction - computational algorithms that evolve in response to the conditions that are being simulated. The reported DSS effort simulated nanoscale transport processes at dopant-defined junctions by coupling electron-phonon and electron-photon scattering mechanisms. Using electronic band structures, phonon band structures, and deformation potentials analogous to silicon <100> material properties, the DSS generated data depicted the dynamic band bending induced by femtosecond variations in applied electric fields.

Correlations between synthesis conditions, phase composition, and spectral properties of the sintered ceramic, thin films and single crystals of EuTa7O19 phosphors have been studied using x-ray diffractometry and temperature dependent photoluminescence (PL) spectroscopy at temperatures between 18 K and 650 K. From the PL spectra of Eu3+, one can obtain information about the area of homogeneity of phases, their temperature transformations, and changes in the bonding character in the neighborhood of the luminescent ion. As a result, this information helps to optimize the synthesis parameters for luminescent materials.

Iron silicide thin films were prepared on insulating substrates using RF magnetron sputtering method. Amorphous, polycrystalline and epitaxial β-FeSi2 were obtained on MgO(001), Al2O3(110) and Al2O3(001) substrates, respectively. Electrical conductivities of these films showed similar temperature dependence. Intrinsic band conduction and hopping conduction mechanism were predominant above and below 600K, respectively. The localized ordering in the polycrystalline and epitaxial films that controled the movement of carriers were as low as in the amorphous film. For the epitaxial β-FeSi2 film, electrical conductivity below 600K were affected by atomic ratio of silicon to iron (Si/Fe) in the films, because the localized ordering in the films decreased as Si/Fe atomic ratio decreased.

Strain modulation of β-FeSi2 by Ge doping was investigated. By solid-phase growth of [a-Si/a-Fe0.4Si0.5Ge0.1]n layered structures, the [a-SiGe/β-FeSi2-xGex]n multi-layered structures (n=1, 2, 4) were formed after annealing at 700 °C. From the analysis of the x-ray diffraction spectra, it was found that β-FeSi1.3Ge0.7 strained by 0.4–0.5 % was formed for the sample with n=1. This value corresponded to the band gap modulation of 30 meV based on the theoretical calculation. The strains decreased with increasing n, which was due to that segregation of Ge atoms from the a-Fe0.4Si0.5Ge0.1 layers to the a-Si layers became significant with increasing n. After annealing at 800 °C, agglomeration of β-FeSi2 occurred, and nanocrystals of relaxed β-FeSi2 and c-Si0.7Ge0.3 were formed. These new structures are useful for formation of opto-electrical devices.

An La1-xSrxGa1-y-zMgyCozO3-(x+y+z)/2 (LSGMCO) has attracted much attention because it can be useable as an electrolyte of a solid oxide fuel cell due to its high oxide ion conductivity. We prepared LSGMCO thin films on silica glass and LaAlO3 single crystal substrates by pulsed laser deposition and evaluated their properties. LSGMCO thin films deposited at 800°C were poly-crystal and the deposition pressure affected their surface morphologies. In the case of the LaAlO3 single crystal substrate, a c-axis oriented LSGMCO thin film was obtained. DC conductivity and complex impedance of LSGMCO thin films were measured in vacuum atmosphere to investigate the effect of the crystal orientation on the oxide ion conductivity. It was revealed that resistance at a grain boundary of films is more dominant compare with the grain interior.

We have studied some key aspects of the (n+)a-Si/(p)c-Si heterojunction structures photovoltaic applications. The importance of the hetero-interface quality has been studied by both theoretical simulations and experimental characterization. The surface treatment prior to the film deposition is very critical. Even though H-plasma passivation can help passivate bulk defects in low quality Si, extreme care should be taken to avoid plasma induced surface damage which will result in a defective hetero-interface. Furthermore, (n+) a-Si films with different doping levels have also been characterized and their influence on the device performance has been studied.

The effects of Ge layer insertion on the solid-phase crystallization (SPC) of a-Si on SiO2 have been investigated. Three types of sample structures, i.e., (a) a-Si/a-Ge/a-Si/SiO2, (b) a-Si/a-Ge/SiO2, and (c) SiO2/a-Ge/a-Si/SiO2, were prepared and annealed at 600°C. For the structure (a) with a thin (∼ 5 nm) Ge layer, Ge atoms completely diffused into a-Si, and SPC was not enhanced. On the other hand, for the structure (a) with Ge layers thicker than 10 nm, Ge atoms were localized at the initial position. Such a localization of Ge atoms was remarkable for the structures (b) and (c) even for samples with thin Ge layers. For samples with Ge localization, significant enhancement of SPC of a-Si was observed. These results indicated that crystal nucleation was initiated in the inserted Ge layers, and then propagated into a-Si. The Ge layer insertion can be employed for positioning of crystal nucleation in SPC of a-Si.

We report on the low temperature growth, by molecular beam epitaxy (375 °C) and electron-beam evaporation (300 °C), of p-Ge films on n-Si substrates for fabricating p-n junction photodetectors, aimed at the integration of opto-electronic components with back-end Si CMOS processing. Various surface hydrogen and hydrocarbon removal treatments were attempted to improve device properties. We invoke Ge diffusion and growth modes as a function of deposition temperature and rate to correlate structural analysis with the device performance.

The present model for current transport at the CdTe/p-ZnTe:Cu/metal back contact assumes that the CdTe and ZnTe valence bands align, while current transport at a highly doped ZnTe and a metal interface proceeds by tunneling. To test part of this model, we have investigated the electrical and material properties of CdS/CdTe devices where the outer metal is either Ti or Ni. Our results show that differences in device series resistance are not linked simply to metal/ZnTe:Cu interfacial contact resistance, but that metallization-induced diffusion remains a more likely cause of significant performance distinctions.

In the metal-induced growth (MIG) process, the poly-Si layer hetero-epitaxially grows from a thin silicide layer, formed by reaction of a metal seed-layer and sputtered silicon, due to an extremely close lattice match between silicon and the metal silicide. The produced poly-Si has shown a promising device quality for photovoltaic applications. Recent results show that the interface of the silicide and poly-Si has a significant effect on the properties of the poly-Si which works as an active layer for photon absorption. In the study of the MIG process, two metals were used as a seed-layer, i.e. Ni and Co. Although CoSi2 has a larger lattice mismatch with Si (1.2%) than does NiSi2 (0.4%), the poly-Si growing from Co has a smoother interface between the poly-Si and silicide, while the one for the Ni seed-layer samples is rather rough. Backscattered XSEM shows that the Ni-contained phase extended into the Si layer by forming long spikes. This might cause crystal defects in the Si layer. The Auger depth profile also showed that the Ni atoms diffuse into the Si layer much more than does the Co. This kind of difference in interface structure causes the different properties of the poly-Si layer. X-ray diffraction (XRD) analysis on the Si layer showed that the Co seed-layer sample had a predominant growth orientation of (220) and the FWHM of 0.2°. The Ni seed-layer samples grew mainly in both <111> and <220> direction, with FWHM of 0.3° and 0.4°, respectively. By comparison, the poly-Si from the Co seed-layer had a higher carrier lifetime of 0.458μs compared to 0.305μs from Ni.

Photoluminescence (PL) of undoped and Sm-doped TiO2, ZrO2 and HfO2 thin films and fibers was investigated at temperatures ranging from 6 to 300 K. The thin films were grown by the atomic layer deposition (ALD) technique and doped by using the ion implantation method. The fibers were prepared by using the sol-gel method whereas an in-situ doping was used to obtain the required concentration of Sm3+ ions in the films. In undoped as well as doped materials, PL was efficiently excited via band-to-band transitions. The emission of undoped materials was attributed to the radiative recombination of self-trapped excitons (STE). In doped materials, intense emission of Sm3+ was recorded. It is proposed, that there exists a concurrence between the radiative recombination of bound excitonic states and the energy transfer to Sm3+ ions, particularly at lower temperatures.