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Traditionally, emphasis has been placed on durable, long-lasting electronics. However, electronics that are meant to intentionally degrade over time can actually have significant practical applications. Biodegradable, or transient, electronics would open up opportunities in the field of medical implants, where the need for surgical removal of devices could be eliminated. Environmental sensors and, eventually, consumer electronics would also greatly benefit from this technology. An essential component of transient electronics is the battery, which serves as a biodegradable power source. This work involves the fabrication, characterization, and modeling of a magnesium-based biodegradable battery. Galvanostatic discharge tests show that an anode material of magnesium alloy AZ31 extends battery lifetime by over six times, as compared to pure magnesium. With AZ31, the maximum power and capacity of the fabricated device are 67 μW and 5.2 mAh, respectively, though the anode area is just 0.8 cm2. The development of an equivalent circuit model provided insight into the battery's behavior by extracting fitting parameters from experimental data. The model can accurately simulate device behavior, taking into account its intentional degradation. The size of the device and the power it produces are in accordance with typical levels for low-power transient systems.

Both WS2 and SnS are 2-dimensional, van der Waals semiconductors, but with different crystal structures. Heteroepitaxy of these materials was investigated by growing 3 alternating layers of each of these materials using atomic layer deposition on 5 cm × 5 cm substrates. Initially, WS2 and SnS films were grown and characterized separately. Back-gated transistors of WS2 displayed n-type behavior with an effective mobility of 12 cm(2) V(-1) s(-1), whereas SnS transistors showed a p-type conductivity with a hole mobility of 818 cm(2) V(-1) s(-1). All mobility measurements were performed at room temperature. As expected, the heterostructure displayed an ambipolar behavior with a slightly higher electron mobility than that of WS2 transistors, but with a significantly reduced hole mobility. The reason for this drop can be explained with transmission electron micrographs that show the striation direction of the SnS layers is perpendicular to that of the WS2 with a 15 degree twist, hence the holes have to pass through van der Waals layers that results in drop of their mobility.

Tin selenide (SnSe) is a two-dimensional, layered metal chalcogenide material. It has a direct band gap, hence has a great potential for next generation of opto- and photovoltaic devices. Uniform, smooth and high quality SnSe thin films were grown over large areas (5cm x 5cm) Si/SiO 2 substrates using Atomic Layer Deposition (ALD). Films were grown over a temperature range of 350°C to 450°C, which exhibit p- type semiconductor characteristics. Structural and optical properties of the as-grown films were investigated using X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). These analyses show growth of 2 dimensional, orthorhombic phase films. Back-gated transistors show p-type conductance, with an average hole mobility of 10 cm2/V.s and I on /I off ratio of ~105. Magnetic analysis shows a paramagnetic behavior.

Physical properties of graphene depend on the number of atomic layers in the film, presence of structural defects and impurities. Low-voltage, aberration-corrected, high-resolution transmission electron microscopy (HRTEM) has proven to be an excellent tool for structure analysis of graphene films. However, experimental observations of graphene films by HRTEM exhibit several challenges due to low contrast and sensitivity of graphene to intense electron beams. While a majority of electron scattering effects in graphene are purely kinematic, the contrast interpretation still requires computer simulations for reliable structure identification. In this paper, we present HRTEM contrast simulations of graphene films based on multislice algorithms and compare them to experimental results. The effects of stacking sequence, number of layers, and presence of impurities have been analyzed in conjunction with imaging conditions.

Heterojunction photovoltaic devices were fabricated using single crystal silicon nanowires and the organic semiconductor regioregular poly-(3-hexyl thiophene) (RR-P3HT). N-type nanowires were first grown on an n+ silicon substrate by the vapor-liquid-solid (VLS) method. Devices were then fabricated by filling the gap between the nanowires and a transparent indium tin oxide (ITO) glass electrode with a polymer. For initial devices the gap was filled with P3HT deposited from chlorobenzene solution. Device performance indicates that both silicon and P3HT act as absorbers for photovoltaic response, but that photocurrents were very low due to high series resistance in the cell. A second type of device was fabricated by depositing a thin layer of P3HT on the grown nanowires by dip coating from a dilute solution, and then filling the voids between nanowires and the transparent electrode with the conductive polymer poly-[3,4-(ethylenedioxy)-thiophene]: poly-(styrene sulfonate) (PEDOT:PSS). The relatively high mob...

Silicon nanowires composed of p-n junctions have been grown on 2 × 5 cm glass substrates with a thin layer of indium tin oxide (ITO). These nanowires were grown both directly on ITO utilizing the vapor-solid (VS) method, as well as by vapor-liquid-solid (VLS) method, with a thin layer of gold as a catalyst. Current-voltage analyses show p-n diode characteristics in both cases. When a reverse dc bias was applied, these diodes responded to optical signals incident on the glass surface, showing potential solar-cell application and intriguing possibilities for future optical detection structures. Devices grown via the VS method displayed better electrical properties compared to those produced via the VLS method.

Metal chalcogenides based on the C–M–M–C (C = chalcogen, M = metal) structure possess several attractive properties that can be utilized in both electrical and optical devices. We have shown that specular, large area films of γ-InSe and Sb2Se3 can be grown via atomic layer deposition (ALD) at relatively low temperatures. Optical (absorption, Raman), crystalline (X-ray diffraction), and composition (XPS) properties of these films have been measured and compared to those reported for exfoliated films and have been found to be similar. Heterostructures composed of a layer of γ-InSe (intrinsically n-type) followed by a layer of Sb2Se3 (intrinsically p-type) that display diode characteristics were also grown.

Thin (∼10 nm) films comprising of Ta2O5–HfO2, Ta2O5–ZrO2, and ZrO2–HfO2 nanolaminates were deposited and characterized for possible gate dielectric applications. These films were deposited on silicon substrates using atomic layer deposition. The dielectric constants of these films were in 12–14 range and the leakage currents in 2.6×10−8–4.2×10−7 A/cm2 range at 1 MV/cm electric field. It was found that as these films were made thinner, the value of their dielectric constant dropped compared to their bulk values. The dominant leakage current mechanism at low electric fields was determined to be Schottky emission, whereas Poole–Frenkel emission dominated at higher fields.

In this work we have investigated the material properties and electrical performance of polycrystalline silicon films formed by an excimer-laser-anneal (ELA) process in different annealing environments. Particularly, we investigated the ELA process in air, nitrogen, argon, and helium and compared it with the standard ELA process in vacuum. Polysilicon thin-film transistors were fabricated using polysilicon material formed by ELA in different environments. We found that while the performance attributes of polysilicon films annealed in vacuum or inert ambient were quite similar, the performance of polysilicon annealed in air was drastically inferior to all. This result was attributed to the increased oxygen incorporation in the film in the case of the ELA process in air. Oxygen increased the density of both deep states and tail states in the polysilicon bandgap. One mechanism, proposed to account for the deterioration in performance, was the oxygen-induced formation of structural deficiencies in grain boundaries and bulk grain regions and its relation to generation of deep-state and tail-state defects.

A thorough investigation of polysilicon films crystallized from amorphous silicon using a XeCl excimer laser has been completed. Emphasis was placed on the development of large crystals, good uniformity, and low surface roughness, with an eye towards improving throughput. This was accomplished through use of SiO2 barrier layers, multiple passes, and careful consideration of annealing ambient. Thermal modeling was performed to help interpret the observed trends and aid in optimization. By controlling these process parameters, samples were produced with a high degree of uniformity and two-dimensional structural ordering, with grains nearly identical in size and stacked in rows and columns. However, a biproduct of the ordering was the creation of large topographical features at the intersection points of multiple grain boundaries, which lead to surface roughness in the range of 12 nm. By applying more shots to the same area, films with maximum grain sizes on the order of 3 μm and reduced surface roughness (6...

Room temperature electroluminescence has been demonstrated from undoped silicon nanowires that were grown from disilane. Ensembles of nanowires were excited by capacitively coupling them to an ac electric field. The emission peak occurred at about 600 nm from wires of average diameter of about 4 nm. The emission appears to result from band-to-band electron–hole recombination.

We have employed first-principles density-functional calculations to study the electronic characteristics of graphene functionalized by metal-bis-arene and metal-carbonyl molecules. It is shown that functionalization with M-bis-arene (M(C6H6)@gr, M=Ti, V, Cr, Mn, Fe) molecules leads to an opening in the band gap of graphene (up to 0.81eV for the Cr derivative), and functionalization with M-carbonyl (M(CX)3@gr, X=O,N; M= Cr, Mn, Fe, Co) up to one 1eV for M=Cr and X=O, and therefore transforms graphene from a semi-metal to a semiconductor. The band gap induced by attachment of a metal atom topped by a functionalizing group is attributed to modification of π-conjugation and depends on the concentration of functionalizing molecules, metal’s and moiety’s electronic structure. This approach offers a means of tailoring the band structure of graphene and potentially its applications for future electronic devices.

The effect of UV laser radiation on the emission of a ZnS:Tb thin film electroluminescent (EL) device has been investigated. It was found that the EL emission can be enhanced near threshold and attenuated at higher voltages by irradiating the device with UV radiation from an argon ion laser. It is shown that these effects are related to the photogenerated carriers that alter transport and build up of charge and the electric field. Both the charge and the field have been determined in real time to examine the enhancement and attenuation of the EL emission.

Atomic layer deposition has been employed to grow nanowires composed of ZnSe/CdSe superlattices. Growth of the nanowires was initiated using gold nanoparticles and the vapor-liquid-solid mechanism. High-resolution transmission electron microscopy shows that these structures are single crystals and the phase of alternating layers of ZnSe and CdSe is zinc blende. The (111) planes of ZnSe and CdSe are oriented at 60°.

We have employed first-principles density-functional calculations to study the electronic characteristics of covalently functionalized graphene by metal-bis-arene chemistry. It is shown that functionalization with M-bis-arene (M=Ti, V, Cr, Mn, Fe) molecules leads to an opening in the band gap of graphene (up to 0.81eV for the Cr derivative), and as a result, transforms it from a semi-metal to a semiconductor. The band gap induced by attachment of a metal atom topped by a benzene ring is attributed to modification of π-conjugation and depends on the concentration of functionalizing molecules. This approach offers a means of tailoring the band structure of graphene and potentially its applications for future electronic devices.

The use of semiconductor nanowires for photovoltaic applications is advantageous for several reasons: 1) it permits interpenetrating networks of materials for semiconductor heterojunctions at the nanoscale, allowing efficient carrier extraction following light absorption, 2) long absorption paths are possible while maintaining short distances for carrier collection, even in imperfect materials, 3) single crystal materials can be grown in relatively thin films with little material, 4) strong light trapping is possible due to the geometry of the nanowires, and 5) manipulation of materials properties is possible by varying the size of the nanostructures. These advantages must be traded off against the difficulties of fabricating devices (particularly planarization of structures), issues with recombination centers at interfaces, and the requirement of making ohmic contacts with relatively low temperature processes. The optical and electronic properties of semiconductor nanowires, nanowire arrays, and heterojunction interfaces are discussed. Recent results for photovoltaic cells based on semiconductor nanorods and nanowires are summarized, and opportunities for improvement of device characteristics are presented.

Si0.5Ge0.5 nanowires have been utilized to fabricate source-drain channels of p-type field effect transistors (p-FETs). These transistors were fabricated using two methods, focused ion beam (FIB) and electron beam lithography (EBL). The electrical analyses of these devices show field effect transistor characteristics. The boron-doped SiGe p-FETs with a high-k (HfO2) insulator and Pt electrodes, made via FIB produced devices with effective hole mobilities of about 50 cm2V−1s−1. Similar transistors with Ti/Au electrodes made via EBL had effective hole mobilities of about 350 cm2V−1s−1.

Dielectrics are used extensively for interlevel insulation in very-large-scale integrated circuits. The planarization of dielectrics has been investigated on single-crystal silicon substrates on which integrated circuits are built. Polysilicon gate or interconnect produces a step of about 0.5 microm which is covered with silicon dioxide (SiO 2 ) to provide insulation. The vertical walls produced by the steps must be made less steep in order to achieve conformal step coverage of a metal film that is deposited on top of this glass. The reduction in the step incline is achieved by reflowing glass that has been made less viscous with dopants such as phosphorus and boron at low temperatures (600–1000°C). Several planarization steps have been examined, including ion implantation, bias sputtering and spin-on glass. Steam was found to be the best ambient, followed by oxygen and nitrogen.

Periodic structures have been obtained during nominally unpolarized excimer laser (ArF)‐assisted organometallic vapor phase epitaxy of GaP on GaAs. Both crystalline properties and chemical composition of these structures have been examined. The chemical analysis showed a variation in composition across a ripple which was attributed to the modulated thermal profile due to interference.

The development of a completely new class of artificially engineered phosphors for electroluminescent displays is proposed in which deep quantum wells embedded in a high band gap material act as radiative centers. The proof of concept of such phosphor activation by quantum wells (QWs) has been demonstrated in the CdSe/SrS multi-quantum well system prepared by atomic layer epitaxy. Various QW widths (3–15 nm) were studied. The reduction in QW width shifts the emission towards shorter wavelength and the emission spectra exhibit multiple peaks, believed to be the result of transitions from several QW levels.

Atomic layer epitaxy has been employed to fabricate white light emitting ZnS:Pr and SrS:Pr thin film electroluminescent devices. Electrical and optical properties of these devices have been characterized and compared. It is found that SrS:Pr devices are significantly brighter and more efficient than ZnS:Pr devices. The effect of ZnS buffer layers on the electrical characteristics of the SrS electroluminescent devices is discussed.

Fabrication of green light emitting ZnS:Tb thin film electroluminescent devices using atomic layer epitaxy is described. In this investigation, particular emphasis is placed on the effect of Tb doping profiles and concentrations on the emission characteristics. It is shown that rapid thermal anneal of these devices has a significant effect on their emission lifetimes.

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

In this work we have co-optimized the deposition and excimer laser crystallization processes for formation of high quality, low-temperature, p-Si films (LPS). We have found that the post-ELA polysilicon structure is very sensitive to deposition process adjustments, collectively expressed by the deposition rate. At low rates the PECVD Si-film is deposited in the microcrystalline phase (µc-Si). Comparing µc-Si and a-Si film precursors, we have shown that at equivalent annealing conditions (laser energy density) polysilicon films obtained from µc-Si precursor demonstrate improved crystallinity (grain size, defect density). Polysilicon thin film transistors (p-Si TFTs) have been fabricated and characterized using this material and compared to our standard process. We have found that the performance of µc-Si precursor exceeds by 20-50% that of a-Si precursor. Use of µc-Si precursor may also have important implications in reducing substrate damage during ELA process and for widening the ELA process window.

We have employed first-principles density-functional calculations to study the electronic characteristics of covalently functionalized graphene by metal-bis-arene chemistry. It is shown that functionalization with M-bis-arene (M = Ti, V, Cr, Mn, Fe) molecules leads to an opening in the bandgap of graphene (up to 0.81 eV for the Cr derivative), and as a result, transforms it from a semimetal to a semiconductor. The bandgap induced by attachment of a metal atom topped by a benzene ring is attributed to modification of π-conjugation and depends on the concentration of functionalizing molecules. This approach offers a means of tailoring the band structure of graphene and potentially its applications for future electronic devices.

Single and multiple layers of graphene films were grown on (111) oriented single crystals of nickel and polycrystalline nickel films using remote plasma assisted chemical vapor deposition. Remote plasma was employed to eliminate the effect of the plasma electrical field on the orientation of the grown graphene films, as well as to reduce the growth temperature compared to conventional chemical vapor deposition. The electrical and optical properties, including high resolution transmission electron microscopy of these films, suggest that this approach is both versatile and scalable for potential large area optoelectronic applications.

Single-crystal SiGe nanowires were synthesized via the vapour-liquid-solid (VLS) growth mechanism using disilane and germane as precursor gases. We have investigated the effect of temperature, pressure, and the inlet gas ratio on the growth and stoichiometry of Si(x)Ge(1-x) nanowires. The nanowires were characterized using scanning and transmission electron microscopies and energy dispersive x-ray analysis. It was found that nanowires with a Si:Ge ratio of about 1 had smooth surfaces, whereas departure from this ratio led to rough surfaces. Electrical properties were then investigated by fabricating back-gated field effect transistors (using a focused ion beam system) where single SiGe nanowires served as the conduction channels. Gated conduction was observed although resistance in the undoped devices was high.

A systematic study of the effects of growth parameters on the morphology and field emission performance of silicon nanowires has been undertaken. Single-crystalline silicon nanowires were synthesized by chemical vapor deposition using indium tin oxide-coated glass as a substrate. Morphologies, internal structures and chemical compositions of the resulting nanowires were analyzed using scanning electron microscopy, transmission electron microscopy and energy-dispersive x-ray spectroscopy. The resulting silicon nanowires possessed a highly ordered single crystalline Si core without an external oxide layer and no obvious indium or tin impurities. For silicon nanowires with growth-times of 5, 10, and 20 mins, the turn-on fields were determined to be 7.4, 7.9, and 11.5V∕μm, while the threshold fields were 9.9, 11.8, and 16.9V∕μm, respectively. Field enhancement factors of 540, 270, and 265 were also calculated while peak emission currents in excess of 25μA were observed for nanowires with 5 min growth-times. T...

A novel design of electrochemical planarization (ECP) system is proposed consisting of a rotating anode, a segmented cathode with very small interelectrode distance, and forced convection. Copper and tantalum anodic polarization curves and steady-state data were collected to validate the electropolishing conditions of the new design. Excellent ECP was produced on patterned electroplated copper films on silicon wafers using this approach.

Ultraviolet photon-induced metalorganic vapor phase epitaxy of CdTe films on GaAs substrates has been investigated using diethyltelluride and dimethylcadmium as the precursor gases. The relationship between the deposition parameters and the properties of the epilayers have been examined using transmission electron microscopy and x-ray rocking curves. Epilayers grown at 6μm/h show an x-ray double-crystal rocking curve full width at half-maximum (FWHM) of 250 arcsec.

A new class of metal ion lasers with significant CW output power in the UV (220-320 nm) and near IR (800-2000 nm) spectral regions is described. In a hollow cathode discharge the upper laser levels are excited via charge transfer collisions between ground state buffer gas ions and ground state metal atoms. At the present stage of development, hollow cathode metal ion lasers are shown to be comparable in UV output power to rare-gas ion lasers but with lower threshold currents by a factor of more than twenty. Visible output powers are lower than rare-gas ion lasers. In the text we present device progress to date, measurements of important plasma parameters, and an outline of potential applications of hollow cathode metal ion lasers.

Ultraviolet photon‐assisted metalorganic vapor‐phase epitaxy has been used to grow CdTe, followed by Hg1−x Cdx Te on GaAs/Si substrates at 250 °C in order to fabricate Hg1−xCdxTe/CdTe/GaAs/Si structures. For Hg1−xCdx Te growth methylallyltelluride, a new Te precursor, is used to obtain growth rates of 4 μm/h. X‐ray rocking curves and transmission electron microscopy are utilized to characterize the crystalline properties of the epilayers and Hall measurements to determine the electrical properties. Hall electron mobilities of Hg1−x Cdx Te (for x∼0.2) are typically 4×104 cm2 /V s at 80 K.

We report a multiline output power of 1 W from the 800.4, 825.5, and 840.4 nm Ag II transitions and 350 mW from the 408.6 nm Ag II transition resulting from pulsed operation of a silver hollow cathode laser. Continuous output of 1 W was obtained in a copper hollow cathode from the 780.8 nm Cu II transition. Design considerations for continuous high-power operation of the hollow cathode discharge are also discussed.

We report multiwatt pulsed (120 μs pulsewidth, 40Hz) laser operation of silver and copper hollow cathode lasers. Peak output powers of 65 mW at 224 nm, 500 mW at 248 nm, 1.3 W at 318.1 nm, and 2.3 W at 478.8 nm have been achieved. Measurements of small-signal gains of selected laser transitions and new laser lines in Cu, Ag, Kr, and Ar are presented.

Rapid thermal annealing of the electroluminescent phosphors ZnS:Mn, SrS:CeF3 and ZnS:SmCl3 has been examined as a function of annealing temperature (500–750°C) and time of exposure (10–120 sec.). The resulting brightness and efficiency of luminescence are correlated with the different processing conditions used. The results indicate that the brightness can be significantly improved from the value obtained with furnace annealing without causing film delamination, blistering or fatigue effect.

This paper briefly reviews the process of UV laser induced thin film deposition, with emphasis on microelectronic applications. The unique aspects of this technique include low process temperatures and spatially selective deposits. Both large area and localized depositions are examined.

An ArF excimer laser was used to photochemically deposit thin films of silicon dioxide, silicon nitride, aluminum oxide and zinc oxide at low temperatures (100-500°C) for microelectronic applications. High depo-sition (>1000 A/Min) rates and conformal step coverage were obtained. The hydrogen bonding, pinhole density, index of refraction, etch rate, and breakdown voltage have been measured for the Si02 and silicon nitride films. The effect of substrate temperature and ArF (193 nm) surface photons on the physical, chemical and electrical properties of Si02 films have been investigated.© (1984) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Laser-induced epitaxial growth of GaP has been achieved using both pyrolytic and photolytic reactions. A focused beam from an argon ion laser operating at 514.5 nm was used to ‘direct-write’ epitaxial microstructures of GaP on silicon using a pyrolytic process. An ArF excimer laser has also been used to demonstrate homoepitaxy utilizing the photolytic process.

Mercury cadmium telluride epitaxial layers have been grown using methylallyltelluride (MATe), dimethylcadmium (DMCd), and elemental Hg. Using these precursors high quality films have been achieved over the temperature range of 200-300°C. Comparisons are made between UV photon-assisted and thermally deposited films. Composition, growth rate, and electrical properties are compared for the two processes under various parameter conditions. Properties of films deposited on various substrates including CdTe, GaAs, and GaAs/Si are also described.

Latchup free CMOS devices have been fabricated by forming PMOS transistors in a 0.5μm thick laser recrystallized silicon layer. This recrystallized layer is isolated fram the bulk wafer by a lμm thick oxide layer. The NMOS transistors were fabricated both in the bulk wafer in the region which was used as the recrystallization seeds, as well as in the recrystallized silicon layer itself. Ring oscillators fabricated with 3μm channel length using a bi-layer lateral CMOS structure show a naninal delay of 1.7ns/stage. The MOS devices fabricated in the recrystallized silicon show low subthreshold leakage current, and surface electron and hole mobilities of 580cm2/V.s and 210cm2/V.s respectively.

Laser oscillation in the infrared has been achieved in a nickel hollow cathode discharge. The 1.3968 µ laser transition is as-signed to Ni I.

We report the deposition of the refractory metals chromium, molybdenum, and tungsten through the laser‐induced gas‐phase photolysis of their respective hexacarbonyls. A copper, hollow cathode laser was used at ultraviolet wavelengths matched to peaks in the absorption spectra of the carbonyl molecules. Localized room‐temperature metal deposition was achieved by focusing the beam into a cell containing the carbonyl gas and helium as a buffer. No major differences were noted for deposition on a polished silicon wafer, a thermally oxidized silicon wafer, and a quartz flat.