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Marcela Mireles,,M.A. Quevedo Lopez 한국물리학회 2016 Current Applied Physics Vol.16 No.11
Thin films of titanium/silicon (Ti:Si) are widely employed in the electronics industry because of their metal-like characteristics. The use of films as thin film resistor (TFR) based on Ti:Si has not yet been reported. In this paper, the TFR characteristics of TiSiON with different compositions and deposited in Argon atmosphere with either 1% Oxygen or 1% Oxygen/3% Nitrogen are studied. The film composition was varied through a co-sputtering approach from titanium and silicon targets and the sheet resistance (Rsh) and temperature coefficient of resistance (TCR) were evaluated. The film composition was evaluated by X-ray photoelectron spectroscopy (XPS); carrier mobility, type and concentration by Hall effect methods and film microstructure by X-Ray diffraction. Nitrogen addition during the deposition reduces oxidized species in the TFR and increases film stability. The addition of nitrogen results in TFR films with partially oxidized titanium and silicon and TFR values closer to zero TCR without impacting film resistance. Films deposited without nitrogen result in more unstable films and larger TCR. A near-zero TCR film was found for a Ti:Si ratio of 1.6, exhibiting a Rsh at 25 C of 0.7 kOhms with a TCR value of 171 ppm/C after annealing at 450 C in forming gas.
Development of CIP/Graphite Composite Additives for Electromagnetic Wave Absorption Applications
우수빈,유찬세,김휘준,이미정,Manuel Quevedo-Lopez,최현주 대한금속·재료학회 2017 ELECTRONIC MATERIALS LETTERS Vol.13 No.5
In this study, the electromagnetic (EM) wave absorption abilityof carbonyl iron powder (CIP)/graphite composites produced byball milling were studied in a range of 28.5 GHz to examine theeffects of the morphology and volume fraction of graphite onEM wave absorption ability. The results indicated that a ballmilling technique was effective in exfoliating the graphite andcovering it with CIP, thereby markedly increasing the specificsurface area of the hybrid powder. The increase in the surface area and hybridization with dielectric loss materials (i.e., graphite)improved EM absorbing properties of CIP in the range of S and X bands. Specifically, the CIP/graphite composite containing3 wt% graphite exhibited electromagnetic wave absorption of −13 dB at 7 GHz, −21 dB at 5.8 GHz, and −29 dB at 4.3 GHz after1 h, 8 h, and 16 h of milling, respectively.
Effects of the Morphology of CIPs on Microwave Absorption Behaviors
우수빈,유찬세,김휘준,이미정,Manuel Quevedo-Lopez,최현주 대한금속·재료학회 2017 ELECTRONIC MATERIALS LETTERS Vol.13 No.6
Electromagnetic (EM) wave absorption properties are affected by thethickness and surface area of absorbing materials. In this study, afacile ball-milling process was introduced to effectively reduce thediameter and increase the aspect ratio of carbonyl iron powder (CIP),which is one of the most commercially available EM-absorbingmaterials. The size, aspect ratio, and consequent surface area of CIPwere manipulated by controlling the milling parameters to investigatetheir effects on EM absorption properties. The results indicated thatball-milled CIPs exhibited better EM wave absorption ability whencompared with that of pristine CIPs. However, significant differencesin minimum reflection loss values were not observed between CIPswith different morphologies and similar specific surface areas. Hence,both fine and flaky CIPs were considered as beneficial for EM waveabsorption.
Carlos Avila-Avendano,Adelmo Ortiz-Conde,Jesus A. Caraveo-Frescas,Manuel A. Quevedo-Lopez 한국전기전자재료학회 2021 Transactions on Electrical and Electronic Material Vol.22 No.4
A novel method for the parameter extraction of thin-fi lm transistors in weak-conduction and triode-region is presented. The parameter extraction is performed using two different and consistent functions based on the integration of experimental output characteristic. The method was tested using measured data of polycrystalline silicon (poly-Si) thin-film transistors (TFTs) and the results were compared with previously reported conventional methods.
Band-gap engineering of Cd<sub>1-x</sub>Zn<sub>x</sub>Te films deposited by pulsed laser deposition
Yoo, S.,Avendano, J.,Delmar, L.,Nam, S.,Quevedo-Lopez, M.,Choi, H. Elsevier Sequoia 2016 THIN SOLID FILMS - Vol.612 No.-
We demonstrate enhanced band-gap tunability in Cd<SUB>1-x</SUB>Zn<SUB>x</SUB>Te thin films (x=0, 0.03, 0.06, 0.1, 0.2, or 1) fabricated directly from Cd<SUB>1-x</SUB>Zn<SUB>x</SUB>Te targets using pulsed laser deposition (PLD). All the Cd<SUB>1-x</SUB>Zn<SUB>x</SUB>Te films have uniform thicknesses of ~200nm, crystalline sizes of ~20nm, and are highly oriented in the [111] direction. The annealed Cd<SUB>1-x</SUB>Zn<SUB>x</SUB>Te targets allow better compositional control of the Cd<SUB>1-x</SUB>Zn<SUB>x</SUB>Te films than non-annealed targets. This new process using a single target with high compositional uniformity provides better tunability of the Cd<SUB>1-x</SUB>Zn<SUB>x</SUB>Te film lattice parameter (6.49 to 6.09A) and band gap (1.48 to 2.22eV) by increasing the Zn concentration (x) from 0 to 1.
Lee, S.,Iyore, O.D.,Park, S.,Lee, Y.G.,Jandhyala, S.,Kang, C.G.,Mordi, G.,Kim, Y.,Quevedo-Lopez, M.,Gnade, B.E.,Wallace, R.M.,Lee, B.H.,Kim, J. Pergamon Press ; Elsevier Science Ltd 2014 Carbon Vol.68 No.-
The performance of graphene field effect transistors fabricated on flexible substrates is easily degraded by deformation, delamination and shrinkage during the device fabrication. Multiple thermal annealing on graphene devices could be performed without damages to the flexible substrate using a rigid supporting substrate, poly(dimethylsiloxane) coated Si, holding the flexible substrate during the device fabrication. As a result, a very high performance including electron mobility ~12980 and hole mobility ~9214cm<SUP>2</SUP>/Vs could be achieved. The performance enhancement is attributed to the effective removal of polymer residues using a high temperature vacuum anneal and a reduced interfacial reaction between the graphene and the hydrophobic flexible substrate.