Modulation of argon pressure as an option to control transmittance and resistivity of ZnO:Al films deposited by DC magnetron sputtering: on the dark yellow films at 10^-7 Torr base pressures

In a previous paper, we reported that thin films of ZnO:Al [aluminum-zinc oxide (AZO)] deposited after achieving a very low base pressure [from 4.0×10-7 Torr (5.6×10-5 Pa) to 5.7×10-7 Torr (7.6×10-5 Pa)] result dark yellow in color and are resistive. These are undesirable characteristics for the application of AZO thin films as front electrodes in solar cells. However, given the increasingly tendency in the acquisition of equipment that allow us to reach excellent vacuum levels, it is necessary to find the deposition conditions that lead to an improving of transmittance without greatly impacting the electrical properties of materials deposited after achieving these levels of vacuum. In this way, the present work is focused on AZO thin films deposited after achieving a very low base pressure value: 4.2×10-7 Torr (5.6×10-5 Pa). For this, we studied the effect of the variation of the oxygen volume percent in the argon/oxygen mixture (by maintaining the deposition pressure constant) and the effect of deposition pressure with only argon gas on the main properties of AZO thin films. The depositions were done at room temperature on glass substrates by direct-current magnetron sputtering with a power of 120 W (corresponding to a power density of 2.63 W/cm2). As results, we found that the variation of deposition pressure with only argon gas is a good option for the control of optical and electrical properties, since the addition of oxygen, although improves transmittance, greatly impacts on the electrical properties. Furthermore, an interesting correlation was found between the optical and electrical properties and the chemical composition of the AZO films, the latter depending on the argon pressure (for this, a careful X-ray photoelectron spectroscopy analysis was performed). Also, the inverse relationship between crystallinity and deposition rate was confirmed, in which deposition rate inversely depends on argon pressure

Leucine supplementation improves adiponectin and total cholesterol concentrations despite the lack of changes in adiposity or glucose homeostasis in rats previously exposed to a high-fat diet

<p>Abstract</p> <p>Background</p> <p>Studies suggest that leucine supplementation (LS) has a therapeutic potential to prevent obesity and to promote glucose homeostasis. Furthermore, regular physical exercise is a widely accepted strategy for body weight maintenance and also for the prevention of obesity. The aim of this study was to determine the effect of chronic LS alone or combined with endurance training (ET) as potential approaches for reversing the insulin resistance and obesity induced by a high-fat diet (HFD) in rats.</p> <p>Methods</p> <p>Forty-seven rats were randomly divided into two groups. Animals were fed a control diet-low fat (<it>n = </it>10) or HFD (<it>n = </it>37). After 15 weeks on HFD, all rats received the control diet-low fat and were randomly divided according to treatment: reference (REF), LS, ET, and LS+ET (<it>n = </it>7-8 rats per group). After 6 weeks of treatment, the animals were sacrificed and body composition, fat cell volume, and serum concentrations of total cholesterol, HDL-cholesterol, triacylglycerol, glucose, adiponectin, leptin and tumor necrosis factor-alpha (TNF-α) were analyzed.</p> <p>Results</p> <p>At the end of the sixth week of treatment, there was no significant difference in body weight between the REF, LS, ET and LS+ET groups. However, ET increased lean body mass in rats (<it>P </it>= 0.019). In addition, ET was more effective than LS in reducing adiposity (<it>P </it>= 0.019), serum insulin (<it>P </it>= 0.022) and TNF-α (<it>P </it>= 0.044). Conversely, LS increased serum adiponectin (<it>P </it>= 0.021) levels and reduced serum total cholesterol concentration (<it>P </it>= 0.042).</p> <p>Conclusions</p> <p>The results showed that LS had no beneficial effects on insulin sensitivity or adiposity in previously obese rats. On the other hand, LS was effective in increasing adiponectin levels and in reducing total cholesterol concentration.</p

Modulation of argon pressure as an option to control transmittance and resistivity of ZnO:Al films deposited by DC magnetron sputtering: on the dark yellow films at 10^-7 Torr base pressures

In a previous paper, we reported that thin films of ZnO:Al [aluminum-zinc oxide (AZO)] deposited after achieving a very low base pressure [from 4.0×10-7 Torr (5.6×10-5 Pa) to 5.7×10-7 Torr (7.6×10-5 Pa)] result dark yellow in color and are resistive. These are undesirable characteristics for the application of AZO thin films as front electrodes in solar cells. However, given the increasingly tendency in the acquisition of equipment that allow us to reach excellent vacuum levels, it is necessary to find the deposition conditions that lead to an improving of transmittance without greatly impacting the electrical properties of materials deposited after achieving these levels of vacuum. In this way, the present work is focused on AZO thin films deposited after achieving a very low base pressure value: 4.2×10-7 Torr (5.6×10-5 Pa). For this, we studied the effect of the variation of the oxygen volume percent in the argon/oxygen mixture (by maintaining the deposition pressure constant) and the effect of deposition pressure with only argon gas on the main properties of AZO thin films. The depositions were done at room temperature on glass substrates by direct-current magnetron sputtering with a power of 120 W (corresponding to a power density of 2.63 W/cm2). As results, we found that the variation of deposition pressure with only argon gas is a good option for the control of optical and electrical properties, since the addition of oxygen, although improves transmittance, greatly impacts on the electrical properties. Furthermore, an interesting correlation was found between the optical and electrical properties and the chemical composition of the AZO films, the latter depending on the argon pressure (for this, a careful X-ray photoelectron spectroscopy analysis was performed). Also, the inverse relationship between crystallinity and deposition rate was confirmed, in which deposition rate inversely depends on argon pressure

Desarrollo de celdas solares basadas en películas delgadas fase2

IP 1101-05-277-97Arbey, Rodriguez, Gerardo Gordillo. -- no. 183 (1998); p.-352360. -- Evolution of the phases and chemical;composition during the formation of CIS thin films prepared byinterdiffusion process in selenides layers / P.;Teheran, Gilberto Cediel, Luz M. Caicedo, Hilderbrando Leal, Jairo Arbey Rodriguez, Gerardo Gordillo. -- En:;Crystal Growth. -- no. 183 (1998); p. 352-360. -- Structural andelectrical properties of DC sputtered;molybdenum films / Gerardo Gordillo, M. Grizalez, L.C. Hernandez. -- En: Solar energy materials and solar;cells. -- no. 51 (abr.-agos. 1998); p. 327-337. -- Estudiodepropiedadescristalograficas de peliculas;delgadas de ZnxCd1 xS y CdSeyS1-y / Giberto Cediel, J. torresLuz m. Caicedo, Hilderbrando Leal, Gerardo;Gordillo. -- En: Revista mexicana de fisica. -- Vol. 3, no. 43(ene.-agos.1998); p. 97-100. -- Estudio de;mecanismos de transporte electrico en peliculas delgadas de SnO2/ H. Mendez, Gerardo Gordillo. -- En: Revista;performance of TCO/CdS/CdTe solar cells / Gerardo gordillo, M.Grizalez, Luis Carlos Moreno, F. Landazabal. --;En: Phys.stat solar. -- (2000); p. 215. -- caracterizacionoptica de peliculas delgadas de CdSxTe1-x;mexicana de fisica. -- Vol. 4, no. 44 (ene.- jun. 1998); p. 17-9181. -- Influence of the optical window on the;depositadas por evaporacion / A. Dussan, J.C. Giraldo y gerardoGordillo.'-- en: Revista colombiana de fisica.; Vol. 32, no. 1 (2000). -- Descripcion del metodo de deposicion de peliculas delgadas de CdSxTe1-x. -- En:;Revista colombiana de fisica. -- Vol. 32, no. 1 (2000). --Resultados y Discusion. -- En: Revista colombiana;de fisica. -- Vol. 32, no. 1 (2000). -- Influence of the oxygenpartial pressure on the opto electrical;properties of ZnO thin films deposited by reactive evaporation/Gerardo Gordillo, J. Olarte, C. Calderon. --;En: Phys. Stat. Solar. -- (2000); p. 293. -- pH effect onthedeposition of CdS on ZnO and SnO: F substrates;by CBD method / Luis Carlos Moreno, J.W. Sandino, N. Hernandez,Gerardo Gordillo. -- En: Phys. Stat. Solar. --;(2000); p. 289. -- PONENCIA(S) EN CONGRESO: Preparation and optpelectroniccharacterization of ZnO thin films;deposited by reactive evaporation / Gerardo Gordillo, C. Calderon, J. Olarte, J Sandino, H. Mendez. -- En:;World conference and exhibition on photovoltaic solar energy conversion. (2 : 1998 Jul. 6-10 : Vienna,;Austria). -- Bogotá : Universidad Nacional de Colombia, 1998.--p. 1-3 ;28 cm.;ARTICULO(S) EN REVISTA: Characterization of CdSxTe1-x thinfilmsthrough thermoelectric power measurements /;C. Jacome, M. Florez, Y. G. Gurevich, J.Giraldo, G Gordillo. --En: Institute of physics publishing. -- no.;34 (2001); p. 1-6. -- Properties of ZnO thin films prepared byreactive evaporation / Gerardo Gordillo, C.;Calderon. -- En: Solmat. -- (2001). -- Characterization ofSnO2thin filmsthrough thermoelectric power;measurements / Gerardo Gordillo, B. Paez, C. Jacome, J.M.Florez. -- no. 342 (1999); p. 160-166.-- Evolution;of the phases and chemical composition during the formation ofCIS thin films prepared by interdiffusion;process in selenides layers / P. Theheran, Gilberto Cediel, LuzM. Caicedo, L. Cota, Hilderbrando Leal, Jair

Desarrollo de dispositivos semiconductores basados en películas delgadas

IP 1101-05-025-92with multilayer structure / G. Gordillo, J. Torres. -- En:ThinSolid Films. -- Vol. 310 (1997); p. 310-316.;'-- Efecto de La temperatura del sustrato sobre La respuesta espectral de fotoconductores basados en peliculas;delgadas de compuestos II-VI (Zn, Cd and S) / G. Gordillo,J.Torres. -- En: Revista Colombiana de fisica. --;Vol. 29, no 2 (1997); p. 131-134. -- Caracterizacion electricade peliculas delgadas semiconductoras de ZnO,;Zno:F y ZnO: Au/Pd / G. Gordillo. ... [et. al]. -- En: RevistaColombianade fisica. -- Vol. 29, no. 2 (1997);p. 139-142. -- Medidas de la respuesta espectral de celdassolares de peliculas delgadas de SnO2/CdS/CdTe / G.;Gordillo, W. de la Cruz. -- En: Revista Colombiana de fisica.--Vol. 29,no. 2 (1997); p. 123-126. --;PONENCIA(S) EN CONGRESO: Surface segregation in CuInSe2 thin films / G. Gordillo, P. Teheran, L. Cota. -- En:;European Photovoltaic Solar energy Conference (1995 Oct :413287: Nice, France). -- Nice, 1999. -- p. -- 28;cm.;ARTICULO(S) EN REVISTA: Preparation and characterization of SnO2thin films deposited by spray pyrolysis;from SnCl4 precursors / G. Gordillo. ... [et. al]. -- En:thinSolid Films. -- Vol. 252 (1994); p. 61-66. --;Preparacion y caracterizacion de peliculas delgadas de CdSdepositadas porel metodo CBD (chemical bath;deposition) / L. Moreno. ... [et. al]. -- En: Revista Colombianade Fisica. -- Vol. 27 (1995); p. 463-466. --;A simple method to determine the optical constants and thicknesses of ZnxCd1-xS thin films / G. Gordillo. ...;[et. al]. En: Thin Solid Films. -- Vol. 289 (1996); p. 238-241.'-- Determination of the optical constants of;policrystalline CdS thin films prepared by evaporation / G. Gordillo. ...[et. al] . -- En: Advances in;Materials Science y Technology. -- Vol. 1, no. 1 (1996); p. 7-12. -- ISSN13162012. -- Preparation and;characterization of CdTe thin films deposited by CSS / G.Gordillo, J. M.Florez, L. C. Hernandez. -- En:;Solar Energy Materials and Solar Cells. -- Vol. 37 (1995);p.273-281. --Evolution of the phases and chemical;composition during the formation of CIS thin films prepared byinterdiffusion process in selenides layers / G.;Gordillo. -- [et. al]. -- En: Journal of cristal Growth. -'- Vol.183 (1998); p. 352-360. -- CuInSe2:;estructura multicapa y sensores de gases tipo taguchi, fabricados con peliculas delgadas de ZnO depositadas;Journal of Physics. -- Vol. 26, no. 1 (Mar. 1996); p. 274-276.-'- Effect of gas chemisorption on the;electrical conductivity of ZnO thin films / G. Gordillo, C. Calderon. -- En: Materials Science y Technology.; Vol. 1, no. 1 (1996); p. 01-05. -- Photoconductors basedonZnxCd1_xS and CdSe1_ySy thin films, fabricate