bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Si/Ge Quantum Well Light-Emitting Diode for Monolithic Integration in Si Photonics Chips
Authors: Saito Shin-ichi , Oda Katsuya , Tani Kazuki , Takahashi Makoto , Nomoto Etsuko , Okumura Tadashi , Suwa Yuji , Lee Yong , Sagawa Misuzu , Sugawara Toshiki , Ido Tatemi
Published: April 2012

A light source made of group IV elements is the only missing device component to realize full monolithic integration on a Si chip to realize the convergence of photonics and electronics by Si photonics. It is well known that Si becomes an efficient light source in quantum confined structures like dots, wires and wells. These nanostructures were previously made by bottom up processes. These days, modern silicon fabrication technology is matured enough to make light-emitting silicon and germanium quantum wells by top down processes. We would like to review our several approaches to develop Si/Ge light sources fabricated in a standard Si process line.
(Invited) Rolled-up 1.55 µm Semiconductor Quantum Dot Tube Lasers
Authors: Mi Z. , Bianucci P. , Dastjerdi M. H. T. , Mukherjee S. , Djavid M. , Poole P.
Published: April 2012

We report on the fabrication and characterization of InGaAsP/InAs quantum dot rolled-up tubes as well as the achievement of a semiconductor tube laser at ~ 1.55 μm. The optically pumped tube laser operates in continuous wave at liquid nitrogen temperature and shows an ultra-low threshold of ~1.26 μW.
(Invited) Particle Size-Dependent Photoelectron Plasmon Loss Features in Deposited Germanium Nanocrystals
Authors: Bostedt C. , Willey Trevor , Franco N. , Terminello Louis J. , Van Buuren T.
Published: April 2012

The plasmon loss features of deposited and well-characterized germanium nanocrystals with average sizes of 3.5 and 4.5~nm, respectively, are investigated with photoelectron spectroscopy at the Ge~3d core level. We observe a particle size dependence of the surface plasmon amplitude with respect to the bulk plasmon consistent with the changing surface-to-bulk atom ratio. Additionally, the nanocrystal surface plasmons are redshifted with respect to a bulk reference by up to 0.4~eV for 3.5~nm particles. For the bulk plasmons no significant size dependent energy shifts can be observed for nanoparticle sizes down to 3.5~nm.
Formation of Photo-Luminescent Patterns on Paper Using Nanocrystalline Quantum Dot Ink and Mist Deposition
Authors: Kshirsagar Aditya , Jiang Zhenyu , Pickering Shawn , Xu Jian , Ruzyllo Jerzy
Published: April 2012

This study explores patterned deposition of cadmium selenide (CdSe) nanocrystalline quantum dot (NQD) thin films on paper substrates using the process of mist deposition. Potential applications of the process include security/anti-counterfeiting patterns and identification labels. Barcode-like patterned NQD films were successfully deposited on a range of substrates, including various types of paper. The films were characterized for fluorescence intensity, spectrum and quality of pattern transfer from shadow mask to the deposited film. Time dependent degradation of the deposited pattern was among key aspects investigated. The results obtained indicate that NQD films deposited on paper and protected against exposure to ambient air using plastic laminate maintain integrity and show negligible degradation in photoluminescence intensity over a period of several weeks.
(Invited) Blue Phosphorescence in Oxidized Nano-Porous Silicon
Authors: Gelloz Bernard , Koshida Nobuyoshi
Published: April 2012

Heavily oxidized porous silicon treated by high-pressure water vapor annealing exhibits a strong blue light emission band which includes a long-lived phosphorescence (Ph) component. This Ph is particularly strong below 200 K. Above 200 K, it experiences a progressive thermally activated quenching. The intensity of the Ph and the peak of its spectrum depend on the excitation energy, and a large Stokes shift was observed. The Ph spectrum included six components exhibiting similar optical properties and likely due to vibronic features of molecular-like species. The Ph was modeled as the result of recombinations from triplet states to ground levels. Its origin is related to silicon nanostructures in an oxide matrix.
(Invited) Designing, Synthesis and Optical Properties of Ultrasmall β-NaYF4 Nanocrystals Doped by Lanthanides Ions for Bio-Medical Applications
Authors: Podhorodecki Artur
Published: April 2012

In this work, structural and optical properties of ultrasmall hexagonal NaYF4 nanocrystals will be discussed as a function of different lanthanide ions combinations.
(Invited) Effects of the Nanostructure and Fabrication Process on the Photoluminescence Properties of PFO Nanopillar Arrays
Authors: Marsal Lluis F. , Palacios Raquel , Formentín Pilar , Santos Abel , Ferré--Borrull Josep , Pallarès Josep
Published: April 2012

Photoluminescent PFO nanopillars are fabricated by replication from nanoporous anodic alumina via template wetting method at room temperature. We have studied how the nanostructure and the experimental process influence the photoluminescent properties of the obtained structures. Results show that the nanoconfinement induces chain alignment in PFO nanopillars and modifies the photoluminescent spectra. The synthesis and characterization of these ordered nanostructures have been developed in order to create a new generation of optoelectronic devices such as polymer light-emitting diodes, sensors and organic solar cells.
Plasma-Driven Transparent Display Panel Using (Y,Gd)BO3:Eu3+ Nanophosphors Prepared by Solvothermal Reaction
Authors: Choi Sungho , Park Byung-Yoon , Seo Jung-Hyun , Yun Young Jun , Jung Ha-Kyun
Published: April 2012

Using uniformly distributed YBO3:Eu3+ phosphors, we demonstrate the emissive luminescent layer applicable to transparent plasma-discharged display panels (PDPs). We prepared uniform and oval-shaped YBO3:Eu3+ particulates by a solvothermal method that were composed of crystalline primary nanoparticles (~10 nm in diameter) and analyzed the particle morphology, luminescence, and after-glow behaviours of the resultant nanophosphors. We fabricated prototype highly transparent PDPs and describe their luminance characteristics regarding optimal process conditions. The resultant YBO3:Eu3+ phosphors with monodispersed shape can be widely used for the luminescent materials of upcoming display devices, such as three-dimensional imaging and transparent displays.
(Invited) Ballistic Electron Emission from Nanosilicon Diode and its Application to Ultra-Thin Film Deposition of Silicon and Germanium
Authors: Koshida Nobuyoshi , Ohta Toshiyuki , Gelloz Bernard
Published: April 2012

A novel wet fabrication technique of quantum-scale Si and Ge thin films is presented based on the ballistic electron effect in solutions. A nanocrystalline silicon (nc-Si) diode, composed of a thin Au (10 nm), nc-Si layer (~1 µm), polycrystalline silicon, and n+-Si substrate, generates ballistic electrons via a multiple-tunneling cascade through a chain of nc-Si dots interconnected with tunnel oxides and ejects energetic electrons from the device surface. A remarkable function of is this nc-Si ballistic emitter is that it operates even in solutions as a supplier of highly reducing electrons. When driven in SiCl4 and GeCl4 solutions without the use of counter electrodes the reducing activity of injected electrons induces the deposition of thin amorphous Si and Ge films on the emission area without producing any by-products and contaminations. Following a brief description of the ballistic emission, the characteristic features of the observed electro-reduction deposition mode is discussed.
(Invited) Electroluminescence in Metal-Oxide-Semiconductor Tunnel Diodes with Nanometer-Thick Silicon
Authors: Morita Mizuho , Tsuchida Ayano , Matsumura Kei , Yamada Ryuta , Oshikane Yasushi , Kawai Kentaro , Uchikoshi Junichi , Arima Kenta
Published: April 2012

Electroluminescence in metal-oxide-semiconductor tunnel diodes with a transparent conductive oxide gate and a nanometer-thick silicon layer on silicon-on-insulator substrates has been studied. The electroluminescence spectra from the diodes are peaked at ~1120 nm (~1.11 eV). The peak shifts toward lower energy as the negative gate voltage value increases. The peak shift can be explained by a Stark effect. The peak tail intensity at the short-wavelength side of the peak at ~1120 nm increases as the silicon layer thickness decreases. This may indicate that the increase in the intensity is due to transitions between subbands near the silicon band edges. Small peaks have been observed at ~1050 nm (~1.18 eV) and ~1010 nm (~1.23 eV). The peak wavelengths are independent of the silicon layer thickness. This exhibits that the electroluminescence is due to defect-mediated transitions.
(Invited) Electroluminescence from Micro-Cavities of Photonic Crystals, Micro-Disks and Rings Including Ge Dots Formed on SOI Substrates
Authors: Shiraki Yasuhiro , Xu Xuejun , Xia Jinsong , Tsuboi Toshiki , Maruizumi Takuya
Published: April 2012

We fabricated Si micro-cavities with Ge dots and successfully observed electroluminescence at room temperature. In the case of micro-disks, we observed both modes of whispering gallery modes and Fabry-Perot modes in photoluminescence, but the latter was found to be well eliminated from micro-rings. For photonic crystals, we observed systematic dependence of PL peaks on the structure parameters such as the diameter and period of air holes and crystal pattern. More than one thousand of Q-factor was observed in these photonic crystals. Well resolved electroluminescence peaks were observed both for micro-disks and photonic crystals at room temperature. However, the line width was found to be much broader than that of PL samples, probably due to the additional metal electrodes, oxide films and doping regions which are not included in PL samples. Moreover, the peak shift to higher energies coming from thermal treatment for diode fabrication was observed.
Desorption of Ge Species during Thermal Oxidation of Ge and Annealing of HfO2/GeO2 Stacks
Authors: Radtke Cláudio , Rolim Guilherme K. , Da Silva Samoel R.M. , Soares Gabriel V. , Krug Cristiano , Baumvol Israel J.R.
Published: April 2012

Thermal stability of HfO2/GeO2 stacks was investigated. These structures were stable on Si up to 600 oC following annealing in N2. Samples prepared on Ge yielded direct evidence of migration and loss of both Ge and O. This contrasting behavior is a result of GeO formation at the GeO2/Ge interface. Desorption of Ge was also observed during thermal oxidation of this semiconductor. The amounts of desorbed Ge were related to the oxygen pressure. Oxygen isotopic tracing results evidenced a strong interaction of oxygen from the gas phase with the already formed GeO2 layer.
VO2, a Metal-Insulator Transition Material for Nanoelectronic Applications
Authors: Martens Koen M. , Radu Iuliana P. , Rampelberg Geert , Verbruggen Jeroen , Cosemans Stefan , Mertens Sofie , Shi Xiaoping , Schaekers Marc , Huyghebaert Cedric , De-Gendt S. , Detavernier Christophe , Heyns Marc , Kittl Jorge A.
Published: April 2012

An overview is given of exploratory Metal-Insulator Transition material based nanoelectronics research at imec and UGent. The VO2 thin film growth techniques used are elaborated. This considers thermal oxidation of vanadium metal and Atomic Layer Deposition (ALD). Fundamental device properties such as voltage driven switching and tunnel junction properties are discussed. Device concepts making use of MIT materials or VO2 are elaborated.
Characterization of Rapid Melt Growth (RMG) Process for High Quality Thin Film Germanium on Insulator
Authors: Zainal Nurfarina , Mitchell S.J.Neil , McNeill David W. , Bain Micheal F. , Armstrong B.M. , Baine Paul T. , Adley David , Perova Tatania S.
Published: April 2012

Germanium is one of the most promising materials for high performance infra-red photovoltaic devices. High quality single-crystal germanium on insulator structures can be produced by a Rapid Melt Growth process. Experiments show that thin-film germanium deposited by physical vapor deposition provides better quality in comparison with chemical vapor deposition. The longitudinal optical Ge-Ge peak in Raman spectrum is shifted from the expected 300.2 cm-1 position due to tensile stress resulting from the thermal expansion differences of the materials. The importance of silicon in the rapid melt process is confirmed by the fact that germanium films on sapphire substrates yielded polycrystalline structure. Films produced at high temperature (980 oC) show full width at half maximum values of 3.3 cm-1 indicating good crystalline quality, comparable to bulk germanium (3.2 cm-1). Thus demonstrating the potential to produce low cost high quality germanium films.
(Invited) New Dielectric Nanomaterials Fabricated from Nanosheet Technique
Authors: Osada Minoru , Sasaki Takayoshi
Published: April 2012

We present a novel procedure for fabricating high-k nanodielectrics by using of perovskite nanosheet (Ca2-xSrxNb3O10) as a building block. We synthesized Ca2-xSrxNb3O10 nanosheets by delaminating layered perovskites (KCa2-xSrxNb3O10), and fabricated multilayer nanofilms on atomically flat SrRuO3 and Pt substrates by Langmuir-Blodgett method. Various microscopy techniques showed highly ordered lamellar structures, and electron energy loss spectroscopy revealed no detectable interdiffusion and strains at the interface between the layers and substrate. These nanofilms showed both high dielectric constant (>200) and low leakage current (< 10-7 A/cm2) even in films less than 5 nm thick. Our work thus provides a new recipe for designing nanodielectrics desirable for future high-k devices.
(Invited) High-k Oxides on InAs 100 and 111B Surfaces
Authors: Lind Erik , Wu Jun , Wernersson Lars-Erik
Published: April 2012

Al2O3 and HfO2 high-k oxides deposited by atomic layer deposition have been studied on InAs 100 and 111B surfaces. By using a low-frequency fitting routine, interface defect densities have been extracted. In general, both HfO2 and Al2O3 show similar Dit profiles, with a Dit minimum around 2×1012 eV-1cm-2.
(Invited) Can Metal/Al2O3/In0.53Ga0.47As/InP MOSCAP Properties Translate to Metal/Al2O3/In0.53Ga0.47As/InP MOSFET Characteristics
Authors: Cherkaoui Karim , Djara Vladimir , O'Connor Éamon , Lin Jun , Negara Muhammad A. , Povey Ian M. , Monaghan Scott , Hurley Paul K.
Published: April 2012

In this paper we present the electrical characteristics of Metal/Al2O3/In0.53Ga0.47As/InP MOS capacitor (MOSCAP) structures formed using a relatively straightforward capacitor process flow and for MOSCAPs which experience the full process flow of an In0.53Ga0.47As n channel MOSFET. From analysis of the capacitance-voltage response over a range of ac signal frequencies fixed oxide charge densities and interface state concentrations are determined for the MOSCAP structures and the impact of forming gas annealing on oxide and interface state densities is presented. The MOSCAP results are compared to the properties of fully processed metal/Al2O3/In0.53Ga0.47As/InP n channel MOSFETs, and the results indicate that the findings from the MOSCAPS do translate to the measured InGaAs MOSFET characteristics.
Comprehensive Demonstration and Physical Origin of HfO2 Gate Stacks: Band Alignment, VFB Shift and Fermi Level Pinning
Authors: Wang Xiaolei L. , Wang Wenwu , Han Kai , Zhang Jing , Xiang Jinjuan , Ma Xueli , Yang Hong , Chen Dapeng , Ye Tianchun
Published: April 2012

Band alignment of TiN/HfO2/SiO2/Si stack is systematically investigated by X-ray photoelectron spectroscopy. The differences of binding energies of Si 2p core level between SiO2 and Si substrate are experimentally found to decrease with the sequence of 5 nm SiO2/Si, 4 nm HfO2/5 nm SiO2/Si and 2 nm HfO2/5 nm SiO2/Si stacks. The p-type Schottky barrier heights at TiN/HfO2 interface of TiN/HfO2/SiO2/Si stack are experimentally estimated to increase with thicker HfO2 thickness. A physical model based on band alignment of TiN/HfO2/SiO2/Si stack is employed to successfully explain these experimental results. The flatband voltage (VFB) of TiN/HfO2/SiO2/Si stack is demonstrated by the proposed model based on band alignment of entire gate stack. The positive VFB shift of TiN/HfO2/SiO2/Si stack and Fermi level pinning are also physically demonstrated by this model and attributed to interface induced gap states at TiN/HfO2 and HfO2/SiO2 interfaces.
Electrical and Optical Characterization of GeON Layers with High-ĸ Gate Stacks on Germanium for Future MOSFETs
Authors: Murad Shahjahan N. , Baine Paul T. , Montgomery John H. , McNeill David W. , Mitchell S.J.N. , Armstrong B.M. , Modreanu Mircea
Published: April 2012

GeON has been investigated as an interfacial layer for high-k gate stacks. Thermally grown GeON layers have been prepared at 550oC and compared with plasma GeON layers prepared at 300oC, The optical band gap of thermally-grown GeON was also determined by spectroscopic ellipsometry to be 4.86 eV. Electrical characterisation of MOS capacitors has yielded interface state densities (Dit) of less than 1012 cm-2eV-1 for all devices using the conductance method.
Mechanism of Difficulty to Study the Physics of Leakage Current Reduction by Nitridation of Silicon before High-k Dielectric Deposition Due to Change in Nucleation Characteristics and Some Other Factors
Authors: Lau Wai Shing
Published: April 2012

It is expected that the leakage current can be reduced by nitridation of silicon before high-k dielectric deposition. In reality, it is not so simple because the nucleation of high-k dielectric on nitrided silicon may be different from the nucleation on silicon. In addition, the interfacial layer between the high-k dielectric becomes thinner because of the nitridation. Furthermore, the bandgap of the interfacial layer becomes smaller due to the nitridation. However, there may be less defect states in the high-k dielectric because of the nitridation. More in-depth study is needed to clarify whether leakage current is really reduced by nitridation. Experimental observation indicates the leakage current can be increased or decreased by nitridation depending on the details of the processing conditions. However, the capacitance is usually increased by nitridation; reduction of capacitance due to RTN is an unusual observation but it is possible.
(Invited) High-Temperature-Operating Dielectrics of Perovskite Oxides
Authors: Ohshima Yumiko , Noguchi Yuji , Oguchi Takeshi , Kitanaka Yuuki , Miyayama Masaru , Torii Shuki , Kamiyama Takashi
Published: April 2012

Perovskite oxides solid solutions of ferroelectric Bi0.5Na0.5TiO3 and hypothetical compound of Ba(Mg1/3Nb2/3)O3, namely (1-x)Bi0.5Na0.5TiO3-xBa(Mg1/3Nb2/3)O3 [(1-x)BNT-xBMN], were synthesized and their crystal structures were analyzed by neutron powder diffraction Rietveld analysis. Structural analysis shows that (1-x)BNT-xBMN constitutes two-phase mixture region composed of rhombohedral R3c and cubic Pm-3m in its phase diagram. Measurements of dielectric, ferroelectric polarization, and electric-field-induced strain properties indicate that (1-x)BNT-xBMN exhibits ferroelectric and piezoelectric properties for x < 0.04 while paraelectric properties for x > 0.05. Dielectric permittivity of (1-x)BNT-xBMN ceramics with x = 0.05 was an extremely high value of 2000-3000 in the high temperature range of 200-400 °C.
SiO2 Thickness Dependency of C-V Dispersion in Stacked Al/HfO2/SiO2/4H-SiC Capacitor
Authors: Hsu Chia-Ming , Hwu Jenn-Gwo
Published: April 2012

The impact of a thin interfacial SiO2 layer inserted between HfO2 and SiC for the improvement of electrical property was investigated. Regarding the material choice of dielectric on SiC, two issues will be presented in this work. One demonstrates the border trap induced C-V frequency dispersion when HfO2 was directly deposited on SiC. The other deals with effect of carbon interstitial or bulk trap in SiC surface close to the SiC/SiO2 interface. The thickness of SiO2 interfacial layer is a critical issue. The defects induced by thicker SiO2 layer would affect the inversion region of substrate. With adopted ultrathin SiO2 (2 nm) layer between HfO2 and SiC, the remarkable frequency dispersion can be significantly reduced. The leakage current with ultrathin SiO2 layer reduced about two orders as compared with only HfO2 on SiC. The reliability of the device with ultrathin SiO2 layer was also improved.
Innovative Gap-Fill Strategy for 28 nm Shallow Trench Isolation
Authors: Tavernier Aurélien , Favennec Laurent , Chevolleau Thierry , Jousseaume Vincent
Published: April 2012

At the 28 nm technology node, the conventional Shallow Trench Isolation (STI) gap-fill process shows some filling limitations due to voids formation in the oxide layer (SiO2), leading to electrical isolation trouble. In this paper, a new gap-fill strategy called L-E-G (for Liner - Etch-back - Gap-fill) is presented. This strategy is based on an innovative etch-back step, using downstream plasma, which allows liner profile reshaping and improves the slope in trenches. First, the etch-back process on blanket wafers is studied. A slowdown phenomenon of the etch rate with plasma exposure time is observed. Then, the relation between plasma conditions and liner profile reshaping is established. Finally, the L-E-G strategy is applied on 28 nm technology wafers. Successful STI void-free is obtained.
Mechanical Damage of Cu/TaOx/Pt Resistive Device Induced by Electric Switching under High Negative Voltage Stress
Authors: Liu Tong , Kang Yuhong , Verma Mohini , Orlowski Marius K.
Published: April 2012

Cu/TaOx/Pt resistive devices can be switched by applying negative set voltages to the Cu electrode when a conductive oxygen bridge is established. When the area of device cell is larger than 100 um2, protrusions are optically observed in the devices during the electroforming process. The protrusion is believed to be the gaseous O2 produced during electro-oxidation reaction of O2- ions on the Pt electrode. For small device areas, protrusions are not observed as the gas may possibly leak out from the perimeter of the cell. The gas protrusion is indicative of O2- migration and the formation of oxygen vacancy nanofilaments in the solid electrolyte.
HfTiON as Charge-Trapping Layer for Nonvolatile Memory Applications
Authors: Huang Xiaodong , Lai P.T.
Published: April 2012

The charge-trapping properties of HfTiON with various Hf/Ti ratios have been studied based on an Al/Al2O3/HfTiON/SiO2/Si structure. The high dielectric constant and high trap density of the HfTiON film induced by Ti incorporation contribute to high performance of the nonvolatile memory device. The memory device with lower Ti content (Hf/Ti = 1/1) exhibits better performance than that with higher Ti content (Hf/Ti = 1/3) in terms of higher program speed (ΔVFB = 4.6 V at +12 V, 100 μs) and better retention property (charge loss of 16.5% after 104 s), mainly due to its smaller gate leakage resulting from appropriate Ti incorporation.
Impact of High-κ TaOx Thickness on the Switching Mechanism of Resistive Memory Device Using IrOx/TaOx/WOx/W Structure
Authors: Prakash Amit , Maikap Siddheswar , Chen W. S. , Lee Heng Yuan , Chen F. T. , Kao M. J. , Tsai M. J.
Published: April 2012

The impact of switching layer thickness on the resistive memory performance and uniformity has been investigated in a simple stack of IrOx/TaOx/W fabricated. The formation of amorphous TaOx and nanocrystalline WOx layers are confirmed from HRTEM image. Bipolar resistive switching memory characteristics with small set/reset and large memory window are observed in all devices after electroforming. The observed TaOx thickness independence of set/reset and low resistance state (LRS) is attributed to the formation of localized nano-filament in TaOx layer. Cumulative probability plot shows tight distribution of LRS. Good data retention with a large resistance ratio of >1e3 at 85oC is obtained.
(Invited) Carrier Transport through Grain Boundaries in Highly Transparent Conductive Ga-Doped ZnO Films
Authors: Yamamoto Tetsuya , Song Huaping , Makino Hisao , Yamamoto Naoki
Published: April 2012

Polycrystalline Ga-doped ZnO films (GZO) with different thicknesses ranging from 70 to 500nm were deposited by ion plating with DC arc discharge at a glass substrate temperature of 200°C. The dominant role of grain boundary scattering in carrier transport in the films is demonstrated by varying the film thickness and grain size. With increasing film thickness, the grain size increases and alignment of the c-axis between the columnar grains is improved. A comparison of Hall mobility and optical mobility shows that for GZO films with thicknesses of above 100nm, carrier transport is mainly limited by grain boundary scattering, whereas for GZO films with thicknesses of less than 100nm, both intragrain scattering and grain boundary scattering are the mechanisms limiting carrier transport. By comparing a grain-size-effect theory with the electrical resistivity data, we obtained that grain boundary reflection coefficients deceases with increasing the grain size.
(Invited) Low-Frequency Noise Reduction in Si Nanowire MOSFETs
Authors: Ohmori Kenji , Feng W. , Hettiarachchi R. , Lee Y. , Sato S. , Kakushima K. , Sato M. , Fukunda K. , Niwa M. , Yamabe K. , Shiraishi K. , Iwai H. , Yamada K.
Published: April 2012

We have investigated the noise spectral density of nanowire and planar FETs. It was experimentally found that the nanowire FET shows lower noise density than the planar FET. By a simulation using Poisson-Schrödinger equations, the distribution of inversion carriers is located further from the interface due to quantum confinement, which well explains the observed lower noise density of nanowire FET.
(Invited) Dry Adhesives for MEMS Assembly, Manipulation and Integration: Progress and Challenges
Authors: Sameoto Daniel
Published: April 2012

Bioinspired synthetic dry adhesives offer unique potential in the field of micro assembly and manipulation. These adhesives, which take their basic operating principle from animals like geckos, use van der Waals adhesion forces and mechanical fiber optimization to produce significant forces. For several years, these materials have been of interest for climbing robots and adhesive surfaces due to potential characteristics like self-cleaning or anti-fouling behavior, anisotropic adhesion strengths and non-transferring materials. These same strengths would make these materials an ideal mechanism for handling delicate parts or manipulating structures in the field of micro-electro-mechanical systems (MEMS) packaging. In this paper, I review the specific fabrication processes developed by our group and examine some of the challenges in their integration with MEMS assembly and packaging processes. Improving normal adhesion strength and directionality of adhesives has been completed and work is beginning to focus on reducing polymer transfer and improving the anti-static compatibility of the structural materials used in the adhesives.
Coaxial-Structured Solar Cells with Silicon Nanostructures
Authors: Li Hung-Hsien , Chen Kuan-Heng , Chiou Si-Ming , Liu Han-Wen , Juan Chuan-Ping , Cheng Huang-Chung
Published: April 2012

Coaxial-structured solar cells with different lengths silicon nanowires (SiNWs) fabricated by e-beam lithography and transformer coupled plasma reactive ion etching (TCP-RIE) were demonstrated in this paper. With the intrinsic amorphous silicon thickness of 15 nm and n-layer thickness of 25 nm, the short-current density and the conversion efficiency of the flat film solar cell were 17.58 mA/cm2 and 3.16 %, respectively. Furthermore, the short-current density increased from 20.75 to 27.90 mA/cm2 and the conversion efficiency increased from 3.59 to 4.69 % when the silicon nanowires length was increased from 0.5 to 1 µm. The proposed coaxial-structured solar cells with SiNWs exhibited nearly 48.42 % efficiency enhancement over the plat film solar cell.
Polysilicon Nanowire Sensor Devices Based on High-k Dielectric Membrane for pH Sensing and DNA Detection
Authors: Wu Chun-Yu , Hsu Po-Yen , Wang Chao Lung , Liao Ta-Chuan , Cheng Huang-Chung , Wu You-Lin
Published: April 2012

The pH sensing characteristics of poly-Si nanowires with high-k sensing membranes are investigated. As a result, the sensing membrane of HfO2 exhibits higher sensitivity and better reproducibility test as compared with TEOS SiO2, Al2O3, TiO2 films. The sensor device with HfO2 dielectric membrane reveals a great pH sensitivity of 172.8 nA/pH. In additon, the label-free DNA detection ability of the poly-Si nanowires is also demonstrated. The 10-base-long single-strained homopolymers DNA molecule solution with an ultra-low concentration of 0.01nM can be detected by using HfO2 sensing film. Such a poly-Si nanowires structure with HfO2 sensing membrane is very suitable for future biochemical sensors applications.
(Invited) Ultrathin Ni1-xPtx Films as Electrical Contact in CMOS Devices
Authors: Zhang Shi-Li
Published: April 2012

Metal silicide films are likely to continue their function as electrical contact in CMOS devices beyond the 22-nm technology node. For such devices, the thickness of the silicide films is projected in the technology roadmap to be below 10 nm. Nickelbased silicides are among the most competitive choices for this application. For this family of silicides, the latest experimental investigations show that upon identical formation conditions (temperature and time), the phase, crystallinity, morphological stability, and thickness of resultant silicide films sensitively depend on the thickness and composition of initially deposited Ni1-xPtx layers. A proper understanding of these experimental observations is instrumental to design and control of ultrathin Ni1-xPtx silicide films with desired properties. In order to achieve low-resistivity electrical contact to Si, dopant segregation technique can be combined with SADS(silicide as diffusion source) processing to modify the Schottky barrier height between the silicide films and the underlying Si.
The Enhancement of Etch Rate of Silicon by Heavy Doping of Phosphorus and Arsenic Atoms during Cyclic Selective Epitaxial Growth of Silicon
Authors: Lee Kong-Soo , Kang Yoongoo , An Ho-Kyun , Jeong Seonghoon , Han Jae-Jong , Kim Bonghyun , Nam Seokwoo , Kang Ho-Kyu , Jeong Hong-Sik , Chung Chilhee , Park Hyunho , Choi Byoungdeog
Published: April 2012

In this study, the enhancement of the silicon etch rate with the heavy doping of phosphorus and arsenic was studied during cyclic selective epitaxial growth process using batch-type equipment. The reaction between molecular chlorine and heavily doped silicon was stimulated during the initial stage of cyclic SEG process at low temperature lower than 700° to induce voids at the interface. Heavy doping of n-type dopants into active regions also brought about the decrease in the growth rate of SEG process. It was possible to attain a stable process window by the elaborate control of total amount ratio of SiH4/Cl2. The window provided the robust interface between SEG silicon and active regions as well as the selectivity to an oxide layer. Vertical diodes which were realized within the window revealed eligible on- and off-current characteristics for cell switches applicable to next generation cross-point memories.
Heterogeneous Chip Integration into Silicon Templates by Through-Wafer Copper Electroplating
Authors: Meyer Christopher D. , Bedair Sarah S. , Trocchia Scott M. , Mirabelli Manrico A. , Benard William L. , Ivanov Tony G. , Boteler Lauren M.
Published: April 2012

This work presents a strategy to enable heterogeneous integration by using electroplated copper as an embedding material to mechanically secure disparate electronic chips within a silicon template wafer. Manual placement of chips into template sockets yielded positional accuracy with <40 μm offset. Temporary facedown attachment of template and chips to a backing surface was utilized to achieve surface planarity with <10 μm topography. The surface of the resulting embedded wafer would be suitable for post-processing to realize interconnects.
(Invited) Integration Challenges of III-V Materials in Advanced CMOS Logic
Authors: Hill Richard J. , Huang Jeff , Loh Wei Yip , Kim Taewoo , Wong M. H. , Veksler D. , Cunningham T. H. , Droopad R. , Oh Jungwoo , Hobbs Chris , Kirsch Paul D. , Jammy Raj
Published: April 2012

The superior transport properties of III-V materials make them attractive choices to enable improved performance at low power. This paper examines the integration challenges of III-V materials in advanced CMOS logic at or beyond the 11 nm technology node, and reports VLSI compatible junction, contact and gate stack process modules with Xj¬<10nm, ND>5x1019cm-3, ρc= 6 Ω.µm2 and Dit = 4 x 1012 eV-1.cm-2.
Heterepitaxial Growth of High Quality Germanium Layer on Si(001)for GOI Fabrication
Authors: Bian Jiantao , Xue Zhongying , Chen Da , Di Zengfeng , Zhang Miao
Published: April 2012

High quality Ge layers on Si(001) have been achieved by two-step heteroepitaxial deposition method using reduced pressure chemical vapor deposition (RPCVD) system. The effect of in-situ hydrogen annealing is investigated. On large Si wafers, the epitaxial Ge layers with TDD less than 1×107cm-2 is obtained. And Raman results indicate that the Ge layers have about 0.17% tensile stress. After successful bonding of the epitaxial Ge layers on Si substrate to a SiO2 wafer, the 6 inch GOI is achieved by Smart-cutTM technology.
Cauchy-Urbach Dielectric Function Modeling of Amorphous High-k LaGdO3 Films
Authors: Pavunny Shojan P. , Thomas Reji , Katiyar Ram S.
Published: April 2012

Optical constants of pulsed laser ablated amorphous high-k LaGdO3 (LGO) thin films on quartz (0001) substrates were measured and analyzed. Refractive indices and extinction coefficients of the LGO layers were estimated to be in the range 2.05 - 2.29 and 0.004 - 0.017, respectively using envelope method. Optical constants were parameterized by analysis of the UV/Visible transmission spectra in the 300 - 750 nm spectral window employing Cauchy-Urbach dispersion model and confirmed the applicability of this model in this wavelength region.
In Situ As2 Decapping and Atomic Layer Deposition of Al2O3 on n-InGaAs(100)
Authors: Ahn Jaesoo , Shin Byungha , McIntyre Paul C.
Published: April 2012

InGaAs(100) channel surfaces that were originally covered with a protective As2 layer are thermally decapped in-situ in a high vacuum atomic layer deposition system prior to Al2O3 deposition. The As2 decapping process is monitored by chamber pressure change and in-situ x-ray photoelectron spectroscopy. A pressure spike is observed during the decapping process and the completion of the As2 desorption is confirmed by a chemical shift in As 3d bonding to the lower binding energy by 0.8 eV. Post-metallization forming gas anneal improves the interface properties and lowers the density of defects at the oxide/InGaAs interface by passivating interface defects and border traps. Thermal evaporation of the gate metal further reduces the frequency dispersion in weak inversion and accumulation compared to the same metals deposited by e-beam evaporation.
(Invited) Calorimetric Studies of the Stability of Perovskites Relevant to Electroceramics
Authors: Navrotsky Alexandra
Published: April 2012

The electrical, magnetic, optical, and transport properties of perovskites are controlled by their structure, which is in turn a consequence of atomic scale interactions that are reflected in their thermodynamic properties. High temperature oxide melt solution calorimetry is a versatile tool for determining such energetics. After an overview of the general thermodynamic factors determining perovskite stability, this contribution concentrates on the thermodynamics of three important systems. The first is BaTiO3-SrTiO3-CaTiO3, where new enthalpy data help separate the effects of cation size and lattice distortion. The second is strontium-doped lanthanum ferrite-manganite (LSFO-LSMO), where defect chemistry, transition metal oxidation state, and magnetism all play important roles. The third is lead magnesium niobate - lead titanate (PMNPT), where short range order, symmetry changes, and competition of other phases (e.g. pyrochlore) are important considerations
Effect of Microstructural Evolution on the Electrochemical Properties of High Performance SOFCs
Authors: Sarikaya Ayhan , Petrovsky Vladimir , Dogan Fatih
Published: April 2012

Microstructures of the component layers play a critical role in the performance of anode supported solid oxide fuel cells (SOFCs). Conventional SOFC configuration composed of laminated and co-sintered NiO-YSZ (yttria stabilized zirconia) anode and YSZ electrolyte and screen printed YSZ-LSM (lanthanum-strontium manganite) was used to investigate the performance of the tailored microstructures. Identification of the polarization mechanisms in half and complete cells allowed improving the microstructural development of the electrodes. Polystyrene demonstrated striking features among the pore formers evaluated to optimize the microstructure of Ni-YSZ anodes. The effects of the composition and sintering temperature on the polarization of YSZ-LSM cathodes were investigated to optimize the cathode performance. The contribution of the electrolyte to the ohmic polarization was lowered by decreasing its thickness. Power densities over 1.75 W/cm2 were measured at 800oC in flowing 10% hydrogen - 90% argon gas mixture on the anode side and air on the cathode side.
(Invited) Transport Properties of Mixed Ionic Electronic Conductors under Thermodynamically Equilibrated Conditions: Measurements on Porous Bodies
Authors: Virkar Anil , Wright James
Published: April 2012

Electrical conductivity, thermoelectric power, and surface exchange coefficient were measured on porous oxide samples. The rationale for using porous instead of dense samples was that porous samples equilibrate with the imposed atmosphere much faster compared to dense samples due to rapid gas phase transport through pores and rapid solid state transport into micron sized particles of porous samples. Experiments were conducted on Gd2O3-doped CeO2 (GDC), Sm2O3-doped CeO2 (SDC), K and Y doped BaZrO3, and Sr-doped LaCoO3 (LSC). Thermoelectric power was also measured on silver for comparison. Chemical diffusion coefficient of oxygen was measured by conductivity relaxation on a dense sample with porous surface layers. The results showed that in all cases, the use of porous samples, or dense samples with porous surface layers, facilitated rapid equilibration and allowed the measurement of properties under thermodynamically equilibrated conditions.
Defect Structure and Defect-Induced Expansion of MIEC Oxides - Doped Lanthanum Cobaltites
Authors: Zuev Andrey Yu. , Sereda Vladimir V. , Tsvetkov Dmitry S.
Published: April 2012

Perovskites based upon substituted LaCoO3-δ are the state-of-the-art materials for a variety of different devices for moderate high temperature applications such as solid oxide fuel cells (SOFCs) and mixed ionic and electronic conducting (MIEC) membranes. The unique feature of the oxides is their ability to undergo both thermal expansion and that induced by the defects of oxygen nonstoichiometry in the oxide lattice. The latter is chemical or defect-induced expansion. This property is extremely sensitive to the defect structure of the oxide material. Therefore reliable data on the defect structure of oxides materials is of key importance to understanding the origin of their chemically induced lattice strain. On the other hand, precisely measured with ppm-resolution chemical expansion of crystal cell of the oxide allows to better understand its local electronic and defect structure.
Metal Phosphates as Intermediate Temperature Proton Conducting Electrolytes
Authors: Huang Yunjie J. , Li Qingfeng , Pan Chao , Anfimova Tatiana , Jensen Jens Oluf , Bjerrum Niels J.
Published: April 2012

A series of metal phosphates were synthesized and screened as potential proton conductor electrolytes for fuel cells and electrolysers operational at intermediate temperatures. Among the selected, niobium and bismuth phosphates exhibited a proton conductivity of 10-2 and 10-7 S cm-1, respectively, under the anhydrous atmosphere at 250 °C, showing close correlation with the presence of hydroxyl groups in the phosphate phases. At the water partial pressure of above 0.6 atm, both phosphates possessed a proton conductivity to a level of above 3 x 10-2 S cm-1. Reasonable stability of the proton conductivity was observed under either a constant low water partial pressure or under a humidity cycling test within a period of more than 80 hours.
Ab Initio Calculation of the Energy Landscape for Protons in DyPO4
Authors: Markus Isaac M. , Adelstein Nicole , Asta Mark , DeJonghe Lutgard C.
Published: April 2012

The rare earth phosphates (REPs RE=La, Ce, Y, Dy, etc) have been identified as possible candidates for intermediate temperature solid oxide fuel cells due to their ability to conduct protons at intermediate temperatures. However, the conductivities between the different REPs vary by up to several orders of magnitude. This suggests that the mechanism of proton transfer might differ between these different compounds because of differences in symmetry or dopant concentrations. Using density functional theory, the lattice parameters and bulk modulus for a DyPO4 unit cell was calculated and compared to experimental values to test the available pseudopotentials in VASP. We also present preliminary findings on the energy landscape for a proton in a DyPO4 unit cell.
Electron Microscopy Study of Single Crystal BaZr0.9Y0.1O3-x Films Prepared by Chemical Solution Deposition
Authors: Lenrick Filip , Griesche David , Kim Jae-Wuk , Schneller Theodor , Wallenberg L.R.
Published: April 2012

Single crystal thin films of 10% yttrium doped barium zirconate (BZY10) have been prepared using chemical solution deposition on magnesium oxide substrates and annealed at 800 or 1000ºC. A focused ion beam lift out technique was used to prepare thin (< 100 nm) specimens for transmission electron microscopy (TEM) analysis. A variety of TEM based techniques were used for characterization, including high resolution imaging, X-ray energy dispersive spectroscopy and energy filtered TEM. High resolution TEM imaging indicated a high quality single crystal film with an epitaxial cube on cube type interface between BZY10 and MgO. For the sample annealed 1000ºC, annular dark field imaging in scanning transmission electron microscopy (STEM) mode showed a layered pattern of lower intensity in the single crystal film. Energy filtered TEM thickness map together with scanning electron microscopy (SEM) indicate the pattern consists of partially repeating voids.
Proton Conduction in Highly Textured Y:BaZrO3 and Y:BaZrCeO3 Thin Films Fabricated by Pulsed Laser Deposition
Authors: Bae Kiho , Choi Sung Min , Hwang Jaeyeon , Son Ji-Won , Shim Joon Hyung
Published: April 2012

Highly textured BZY and BZCY films were fabricated on a single crystalline MgO(100) substrate by PLD under various deposition conditions including substrate temperature and target-to-substrate distance. The perovskite-type oxides, BaZr0.85Y0.15O3-δ (BZY) and BaZr0.3Ce0.55Y0.15O3-δ (BZCY), were synthesized via a solid-state reaction method and sintered at 1680° to be used as targets for pulsed laser deposition (PLD). The structural properties of the films were analyzed by x-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrical conductivities of the films were measured by the electrochemical impedance spectroscopy (EIS) method in the temperature range of 220-460°.
Grain Boundary Blocking Effect in Yttria Stabilized Zirconia Thin Films
Authors: Schlupp Meike V. , Ma Huan , Martynczuk Julia , Prestat Michel , Gauckler Ludwig J.
Published: April 2012

The cross-plane oxygen ion conductivity of yttria stabilized zirconia thin films prepared by aerosol assisted chemical vapor deposition is strongly influenced by the thin film microstructure. Thin films with highly textured columnar grains oriented parallel to the current direction exhibit significantly higher conductivity than thin films with randomly oriented nanocrystalline microstructure, where ionic transport proceeds through the numerous grain boundaries. The total conductivity of columnar AA-CVD thin films is consistent with literature values on oxygen ion conduction through chemically pure YSZ grains as determined for microcrystalline samples, while that of the nanocrystalline specimens is similar to corresponding specific grain boundary conductivities.
Grain and Grain Boundary Conductivities in Nanocrystalline Yttria-Stabilized-Zirconia Thin Films
Authors: Scherrer Barbara , Grolig Jan G. , Prestat Michel , Gauckler Ludwig J.
Published: April 2012

Nanocrystalline yttria-stabilized-zirconia thin films with grain sizes smaller than 15 nm are fabricated by spray pyrolysis. Impedance spectroscopy is performed perpendicular to the thin film between room temperature and 600 °C. For a grain size of 13 nm, the grain and grain boundary contributions of the electrical conductivity can be discerned but only between 200 °C and 400 °C. For smaller grains, and higher or lower temperatures, the grain contribution cannot be resolved.
Nano-Structuring of SOFC Anodes by Reverse Current Treatment
Authors: Klotz Dino , Szasz Julian , Weber André , Ivers-Tiffée Ellen
Published: April 2012

The electrooxidation reaction in the Ni/YSZ anode is still a limiting factor for the performance of anode supported SOFCs (ASC). An effective method for the improvement of anode performance is based on a short-time application of a high current density in reverse direction (reverse current treatment, RCT). In this contribution we evaluate this in-situ method for different oxygen partial pressures, current densities, durations, and the number of treatments. New information on the interplay between formation parameters and nanostructure characteristics is provided, giving new insights on nano-structuring of SOFC anodes.
Electrochemical Oxygen Reduction on LaNi0.6Fe0.4O3-δ Film Electrode
Authors: Budiman Riyan A. , Hashimoto Shin-ichi , Amezawa Koji , Kawada Tatsuya
Published: April 2012

Electrochemical oxygen reduction on an LaNi0.6Fe0.4O3-δ (LNF) dense film electrode was investigated by using AC impedance spectroscopy as functions of temperature (923~1073 K), oxygen partial pressure (10-3~1 bar), and DC bias (-50~+20 mV). It was found the oxygen reduction reaction on the LNF electrode is rate-controlled by the absorption and the dissociation of oxygen molecules at the surface, although other elementary reactions also might contribute to the total reaction rate. 18O isotope exchange and its depth profile measurements by using a secondary ion mass spectrometry (SIMS) were performed to give quantitative analysis for the rate determining step (RDS) on LNF. The conclusion derived from the SIMS measurements was in good agreement with that from the electrochemical measurements, showing that the surface reaction is a major cause of the resistance in the LNF electrode but the bulk diffusion also may contribute to the reaction rate.
Influence of Gadolinia-Doped Ceria Buffer Layer on the Durability of LSCF/CGO/YSZ System for IT-SOFC
Authors: Constantin Guillaume , Rossignol Cécile , Briois Pascal , Billard Alain , Barnes Jean-Paul , Dessemond Laurent , Djurado Elisabeth
Published: April 2012

Interfacial reactivity between CGO layer and YSZ substrate was characterized by ToF-SIMS depth profiles and XRD. No reactivity between CGO and YSZ was detected after heat treatment at 800 °C for 2 h in air. Whereas, after 1500 °C for 10 h in air a solid solution was detected in homogeneous composition, with low Ce and Gd content, at least on 6 µm. An ageing investigation at 700 °C of LSCF/CGO/YSZ half cell was performed for different CGO buffer layer thickness (0, 0.45 and 2 µm), using EIS. Electrical properties of the half cell are dependent on the CGO thickness.