Jorge Aguilar

In this work, a study of the physical properties of commercial single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) synthesized by the microwave method and processed by spray-coating method on aluminum-doped zinc oxide (ZnO:Al, AZO) substrates and their potential application as transparent front electrode or electron t...

This work presents research results concerning to the fabrication of hybrid solar cells in a superstrate configuration with the following structure: glass/SnO2:F/ZnO + CdS/CdTe + CdCl2-TT/PEDOT:PSS-TT/Cu-Mo. After Cadmium Telluride (CdTe) absorber layer processing, the organic conjugated polymer Poly(3,4-ethylenedioxythiophene): poly(styrene sulpho...

In this study, we use the Haacke´s Figure of Merit (FOMH) as a valuable parameter for determining suitable Indium Sulphide thin films among a set of samples processed with different deposition parameters, in order to use them as window layers in the usual configuration of photovoltaic devices. Two sets of In2S3 thin films were deposited by radiofre...

A study of transparent thin films of Zinc Oxide doped with Aluminum (AZO) processed by sputtering with potentials application as substrate for single wall carbon nanotubes processing by spray-coating is discussed in this work. AZO Thin films have been deposited by radiofrequency magnetron sputtering technique at room temperature in high vacuum ambi...

CdS1-xSex films are deposited by chemical bath (CBD) onto corning glass, varying the composition x from 0 to 1, at 50 ℃, 75 ℃, and 90 ℃ for deposition times going from 5 to 180 min. Concentrations and ratios of precursors are modified to obtain the respective nominal film composition. Analysis through atomic force microscopy (AFM) and Raman scatter...

In this work we present a study of optical, structural and chemical properties of semiconducting CdSe nanoparticles with an organic shell prepared by laser fragmentation of acetone dispersed CdSe powder. A Nd-YAG pulsed laser of 50 Hz frequency repetition and tuned at the first and second harmonic, λ = 1064 and 532 nm, was used for the ablation. Th...

In this work we developed the synthesis and characterization of Sb2Te3 thin films, which were grown by RF as well as DC sputtering as a function of the deposition pressure (Pd), 5–15 mTorr. Sb2Te3 films were characterized through X-Ray Diffraction, Energy Dispersive Spectrometry (EDS), Scanning Electron Microscopy (SEM) and electrical resistivity m...

The present study is based on the processing of polyaniline fibers by electrospinning using polyethylene oxide as a stabilizing agent for textile fiber. Polyaniline was doped with camphorsulfonic acid in different percentages to evaluate its influence on the electrical conductivity. In this study, fibers were made from a solution of polyethylene ox...

Silicon thin films were prepared by Laser Ablation technique onto fused quartz substrates. The effect of thermal annealing on the silicon films and the pressure and temperature dependence show an unusual behavior of photoluminescence (PL) spectra of the silicon (Si) thin films. An intense PL energy band around 3.0 eV (400 nm) was observed at room t...

In this work, we present the preparation of CdS nanowires (CdS NWs) using the chemical vapor deposition technique and bismuth (Bi) nanoparticles as catalysts. The obtained nanowires were found to be in the hexagonal Greenockite structure according to XRD diffractograms and Raman spectroscopy measurements. Depending on the growth temperature, two ki...

CdS1-xSex thin films were deposited by Chemical Solution onto ITO/glass substrates at 90 °C. Structural, optical and photoelectrochemical properties of the ternary solid solution films were evaluated in this work. The results revealed good crystalline quality of the CBD films as an effect of ITO substrate and deposition temperature. Additionally, t...

Polycrystalline thin film CdS has been used as window material in photovoltaic solar cells. Its ideal band gap (2.45 eV), low resistivity and electron affinity made this material the most used in photovoltaic engineering; However, nowadays a cadmium free material with similar properties is necessary. β-In2S3 has shown adequate physical properties t...

Magnetron Planar Sputtering (MPS) is an appropriate deposition technique for ultrathin (UT) solar cells fabrication. This technique is compatible with deposition of many materials which are relevant for the preparation of thin film cells, including p-type CdTe and CuInGaSe2, and n-type CdS as a window partner material. Therefore, MPS enables the se...

Undoped cadmium selenide nanoparticles (CdSe-NP's) were grown on glass substrates by chemical bath synthesis (CBS). The particle size was controlled by means of the bath temperature (Tb), which was chosen within the interval 0–80 °C. X ray diffraction patterns indicate that CdSe-NP's grow in the hexagonal wurtzite (WZ) crystalline phase for low Tb...

In this work we present results and analysis concerning the processing and characterization of Gallium Nitride (GaN) thin films (TF) grown on Si (111) substrates by pulsed laser deposition technique (PLD), which were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) and Raman spectroscopy (RS). The GaN...

In2S3 thin films are prepared by chemical bath deposition (CBD) technique to be applied as buffer layer in CdTe solar cells. CdTe photovoltaic devices are developed using In2S3 as “standard buffer layer” in order to reduce the CdS thickness used as window material. It is important to examine potential thin films in a prospective life cycle study, f...

Ammonobasic reactive sublimation (ARS) is proposed as a novel method to synthesize GaN and related oxides. Results indicate that GaN growth occurs by a nitriding process of Ga and related oxides, establishing a direct dependence on NH4OH amount added as a primary chemical reactive. The samples were grown on p-type Si (111) substrates inside a tube...

CdSe and CdS0.25Se0.75 thin films were grown by the Chemical Bath Deposition technique at different temperatures (50-90°C) and deposition times (5-180 min). Both kinds of films are polycrystalline, constituted by nanostructured clusters of particles. CdSe films consist in a mixture of cubic and hexagonal phases (4-8 nm crystal size), whereas only t...

Chemical Bath Deposition (CBD) was used to grow CdS1-xfSexf (xf = 0.5) thin films on Corning glass substrates at 75 C. The atomic composition of the bath was varied until an xf of 0.5 was obtained, maintaining the deposition time at 120 min. Then the deposition time was modified from 5 to 360 min. The structural and optical properties of the films...

The effect of depositing CdS nanoparticles on the surface of a high temperature superconductor Bi-Pb-Sr-Ca-Cu-O is investigated by means of magnetically modulated microwave absorption spectroscopy (MAMMAS), for the 77-300 K temperature range. The experimental results indicate that the onset of superconducting transition in Bi-Pb-Sr-Ca-Cu-O/CdS comp...

CdS and CdS0.75Se0.25 thin films were prepared at different deposition time (5-180 min) and at 75 °C by Chemical Solution Deposition. All the films are polycrystalline in nature; in the case of CdS, a mixture of cubic and hexagonal phase is present whereas the CdS0.75Se0.25 films show hexagonal phase. The CdS films are dense and homogeneous with go...

CdS1−xSex thin films were deposited on Corning glass substrates at 75 °C by chemical bath deposition (CBD) varying the composition “x” from 0 to 1 at a constant deposition time of 120 min. The composition of the films was adjusted by modifying the concentration as well as the ratio of the precursors. The morphological, compositional, structural and...

In this paper we present results concerning the processing and characterization of polyaniline microfibers obtained by the electrospinning technique. The electrospinning technique is used to produce micro and nano fibers, this technique uses an electric field to stretch the jet of the polymer and thus produce fibers, which are deposited on a collec...

Micro and nano-fibers from polymers in solution can be easily obtained by using the so called electrospinning technique. The principle of this technique relies on applying a positive voltage to the polymer solution and a negative voltage to a collector. By increasing voltage, the surface tension will be overcome and will eject some kind of fiber de...

We present in this work results on semiconductor nitride thin films as grown by Close Space Vapor Transport (CSVT) and Laser Ablation (LA). The films were processed in different substrates and were characterized by X-Ray Diffraction, Scanning Electron Microscopy, Energy Dispersive Spectroscopy, Transmission Electron Microscopy (TEM) and Photolumine...

Photoluminescence (PL) studies in GaN thin films grown by infrared close space vapor transport (CSVT-IR) in vacuum are presented in this work. The growth of GaN thin films was done on a variety of substrates like silicon, sapphire and fused silica. Room temperature PL spectra of all the GaN films show near band-edge emission (NBE) and a broad blue...

Raman scattering (RS) is a very important experimental tool to characterize the optical modes and another elementary excitations of materials. Among other issues it can determine for example the degree of crystalline quality and point defects like local modes. Therefore GaN - thin films and related compounds for photovoltaic purposes and as process...

We present in this work experimental results and their analysis concerning the structural and optical characterization of cadmium selenide (CdSe) films grown by the Chemical Bath Deposition (CBD) technique, at different bath temperatures Td : 0≤Td≤80 °C. Structural characterization was carried out by using X-ray diffraction, whereas optical charact...

Cadmium Selenide (CdSe) thin films were prepared by pulsed laser deposition using a Nd:YAG laser (355 nm). Films were grown by ablating a sintered pure CdSe target with fluences from 0.1 to 1.5 J/cm2 on corning glass, silicon (100) and quartz substrates. Deposition chamber was maintained under vacuum pressure while substrate temperature was increas...

We present in this work some results concerning the effects of the thermal annealing with CdCl2 on the optical properties of CdS thin films grown by radio-frequency planar magnetron sputtering technique, under optimized growth parameters: gas pressure, atmosphere, substrate temperature, power of plasma, etc. An improvement of the optical properties...

We present in this work the characterization studies carried on GaN - thin films as processed by the Close Spaced Vapor Technique (CSVT), Laser Ablation (LA), and Molecular Beam Epitaxy (MBE), under particular growth parameters for each of the three techniques. The films characterization was performed by x-ray diffraction (X-RD), Photoluminescence...

A 24-pair Si-rich SiN x /SiO x -based distributed Bragg reflector (DBR) architecture, in situ doped with Si nanocrystals (Si-ncs), is studied to show self-photoluminescence (PL) with narrow-linewidth green-color emission pattern. By cascaded depositing, the broadband luminescent SiN x /SiO x pairs with SiN x and SiO x layer thickness of 45 and 86 n...

We present in this work studies of photoluminescence at room temperature, AFM and optical transmission measurements of Cadmium Sulphide (CdS) films grown by the Closed Space Vapor Transport (CSVT) technique. Normally as-grown CdS-CSVT thin film samples do not show luminescence at room temperature, due mainly to the high density of deep non-radiativ...

Silicon nanocrystals embedded in silicon nitride films were grown by direct plasma enhanced chemical vapor deposition at 300 degrees C, using mixtures of SiH2Cl2/NH3/H2/Ar. The films composition and chemical stability was tested by Fourier Transform Infrared Spectroscopy and Rutherford Backscattering Spectroscopy. The influence of hydrogen abundanc...

We present in this work the fabrication of photovoltaic modules of the CdS/CdTe type, the first ones processed in Mexico in large area (40 cm2 and contact area of 3 cm2); these photovoltaic modules are constituted of the n-type cadmium sulfide (CdS) semiconductor, as the window material, and the p-type cadmium telluride (CdTe) semiconductor as the...

A preliminary study of the electrochemical synthesis and optical characterizacion of the conducting polymer polypyrrole (PPy) was carried out, in order to understand the in-situ electropoliymerization of PPy. Electropolymerization was performed in a three electrode cell by using freshly prepared monomer solutions in presence of a side-coupler agent...

Textile 100 % acrylic fabrics have been used in tapestry for a long time. One of the drawbacks of this type of fabrics is its great flammability. Textile fabrics are coated with flame retardant in order to reduce the flammability. We present some results concerning the use of commercial products (Flame-Out, Borax (Na2B4O5(OH)4•8H2O), and Hexametaph...

Cadmium selenide thin films were prepared by chemical bath deposition (CBD) and pulsed laser deposition (PLD) methods. For CBD films, cadmium chloride (CdCl2) and cadmium acetate (Cd(CH3COO)2) solutions were employed as Cd2+ source while a freshly prepared sodium selenosulfite (Na2SeSO3) solution provided the Se2− ions. The pH of the bath was adjus...

We present in this work preliminary studies concerning the optical characterization, by optical absorption, photoluminescence and Raman spectroscopies, of Si-enriched films into a SiO2 matrix as a function of the Si concentration. The Si-molar concentration dependence shows different characteristics for each one of the samples: low Si concentration...

The physical properties of Bi doped CdTe films, grown on glass substrates by the Closed Space Transport Vapour (CSVT) method, from different Bi doped CdTe powders are presented. The CdTe:Bi films were characterized using Photoluminescence, Hall effect, X-Ray diffraction, SEM and Photoconductivity measurements. Moreover, CdS/CdTe:Bi solar cells were...

In previous papers we have reported the improvement of the efficiency of CdS/CdTe solar cells by varying the thiourea/CdCl2 ratio (Rtc) in the chemical bath solution used for the deposition of the CdS layers. In this work, a more complete study concerning the physical properties of Chemical Bath Deposited (CBD) CdS layers studied by photoluminescen...

The photoluminescence (PL) of silicon nanoclusters embedded in silicon nitride films grown by remote plasma-enhanced chemical vapor deposition at 200 °C, using mixtures of SiCl4/H2/Ar/NH3 is investigated. It was found that the color and the intensity of the PL of the as-grown samples depend on the H2 flow rate, and there is an optimum flow for whic...

In this work, nanocrystalline silicon (nc-Si) embedded in amorphous silicon nitride (a-SixNy) films have been characterized by High Resolution Transmission Electron Microscopy (HRTEM). The films have been grown by remote plasma enhanced chemical vapour deposition (RPECVD) onto silicon substrates using a mixture of SiCl4, NH3 and H2. Subsequently, t...

Strong white and blue photoluminescence (PL) from as-grown silicon nanocrystals (nc-Si) in SiNx films prepared by remote plasma enhanced chemical vapour deposition using SiCl4/NH3 mixtures is reported. The colour and intensity of the PL could be controlled by adjusting the NH3 flow rate. Samples with white emission were annealed at 1000 °C, obtaini...

A study of the physical properties of CdTe thin films doped with Bi is presented. CdTe:Bi thin films were deposited by the close space vapor transport (CSVT) technique using powdered CdTe:Bi crystals grown by the vertical Bridgman method. CdTe:Bi crystals were obtained with nominal Bi doping concentrations varying in the 1×1017–8×1018 cm−3 range. T...

Usually as-grown chemical bath deposited Cadmium sulfide (CdS) samples do not show luminescence at room temperature because of the high density of recombination centers due to many defects generated during the growth process, particularly for chemical bath deposited CdS films. The change of the S/Cd ratio allows to control the density of defects gi...

In this work, we present studies of photoluminescence at room temperature of CdS films grown by the chemical bath deposition technique. Usually, as-grown CdS-CBD samples do not show luminescence at room temperature because of the high density of recombination centers due to many defects generated during the growth process. The change of the S/Cd ra...

In this work, we study CdS films processed by chemical bath deposition (CBD) using different thiourea concentrations in the bath solution with post-thermal treatments using CdCl2. We study the effects of the thiourea concentration on the photovoltaic performance of the CdS/CdTe solar cells, by the analysis of the I–V curve, for S/Cd ratios in the C...

For optimizing and having reproducibility of the PV-performance of CdTe based solar cells, the quality of the CdS-partner window material plays an important role. One of the main problems to be solved consists in eliminating the pinhole density in the CdS layer, as well as its processing with the suitable geometric granularity (grain size, roughnes...

We have grown CdS films by the Close Spaced Vapor Transport technique under specific conditions: substrate temperature (Ts): 450°C, source temperature (Tso): 725°C, argon pressure in the chamber (PAr): 100, 200 and 500mT, deposition time (td): 100s. The films were studied by measuring the luminescence properties at different temperatures in the ran...

We have investigated the influence of the microstructure and chemistry of the surrounding host on the strong visible photoluminescence (PL) from silicon nanoclusters (nc-Si) embedded in three different silicon-based dielectric compounds: SixNy:H,Cl, SixNyOz:H,Cl, and SixOz:H,Cl, obtained from silicon nitride films deposited by SiH2Cl2/NH3/H2 plasma...

We present results on secondary ion mass spectrometry (SIMS) and mu-Raman spectroscopy measurements, carried out in each one of the layers conforming the CdTe based solar cells of the type: soda-lime glass/SnO2:F/CdS/CdTe/Cu:Au, in order to get the atomic and vibrational characteristics of the different layers and their correlation, with the use of...

Evidences of the passivation effect are given when thin films of CdS are deposited on GaSb crystalline substrates, using a bath chemical deposition method. The passivation process is studied through photoacoustic and photoluminescence experiments. The surface recombination velocity calculated from photoacoustic measurements decreases and the radiat...

Very thin layers of Si were grown in between silicon nitride layers using Plasma Enhanced Chemical Vapor Deposition (PECVD) technique and SiH2Cl2/H2/NH3 mixtures. Deposition conditions were selected to favor Si cluster formation. Room Temperature Photoluminescence (RT-PL) and optical transmission in different ranges were used to evaluate the optica...

In this work we present results about the influence of a postdeposition heat treatment with CdCl2 on CdS films grown by the Close Spaced Vapour Transport (CSVT) technique. Such heat treatment has been used as a standard procedure to improve the overall performance of CdTe/CdS based solar cells. The films were studied by analyzing the luminescent pr...

Cadmium sulfide films of different thicknesses were deposited by chemical bath deposition (CBD) from a bath containing cadmium chloride, ammonium chloride, ammonium hydroxide and thiourea. The XRD patterns show that the films have a hexagonal phase with a preferential (002) orientation. The photoluminescence spectra show a defect structure, charact...

Photoluminescence (PL) spectra of CdTe at low temperatures usually show a narrow band at 1.55 eV, sometimes together with phonon replicas. It has been shown that this band is associated with a transition involving an acceptor level due to a cadmium vacancy; however, there is discrepancy about the high-energy level which causes this transition. It i...

Photoluminescence (PL) spectra of CdTe single crystals and films, undoped and Ag-doped, were studied in the range of the photon energy (hν): 1.5–1.6 eV, at 10 K. Films were doped during the growth process. Thin layers of Ag were vacuum evaporated onto the surface of undoped CdTe crystals, then were submitted to thermal annealing in a N2+2% H2 ambie...

Investigations of photoluminescence, its temperature dependence, Raman scattering and IR absorption spectra were done for the study of the photoluminescence mechanism in porous silicon and Si enriched silicon oxide films. Red (1.6-1.7 eV) and orange (1.9-2.2 eV) photoluminescence bands are observed in both objects. Comparative investigations indica...

Photoluminescence (PL) and Raman spectra of silicon oxide films enriched by Si or Ge have been investigated before and after thermal annealing at 1150degreesC and 800degreesC, respectively. The dependences of PL peculiarities on the concentration of Si and Ge, as well as on the existence (or absence) of Si (Ge) quantum dots in silicon oxide films a...

This paper presents the results of a photo luminescence investigation of silicon oxide films enriched by Ge. Photoluminescence peculiarities are analyzed both for "as prepared" silicon oxide films enriched by Ge (without Ge-nanocrystalls) and for films with Ge-nc, created during film annealing in inert atmosphere at 800degreesC. Raman scattering sp...

In this paper, we present a comparative study of photoluminescence and its relation to the structural properties of cadmium sulphide (CdS) thin films grown by chemical bath deposition (CBD), close spaced vapour transport, laser ablation (LA) and sputtering. Taking into account that the physical properties of CdS thin films depend upon the growth te...

Thin films of CdS with different nominal ratios c (thiourea)/c (CdCl2) have been grown by conventional chemical bath deposition on an InP substrate, in order to study the influence of each film on the surface passivation of the InP sample. The values of the surface recombination velocity were determined by the photoacoustic technique (PA) and photo...

An adhered organic deposit, formed within the petroleum well on the steel surface of the tubing walls, was systematically characterized following a sequence of bulk and surface techniques. The results allowed the identification of the tubing wall and its internal surface structures. As a consequence of the contact with sulphur-bearing compounds suc...

Photoluminescence spectra and their dependence on temperature as well as Raman scattering spectra and Atomic Force Microscopy investigations have been used to study the peculiarities of the red photoluminescence band in low-dimensional Si structures, such as porous silicon and silicon oxide films. It has been shown that the red photoluminescence ba...

We present in this work the processing of large area CdS and CdTe thin films. We have been working for this purpose with a Radio-Frequency Planar Magnetron Sputtering (RF-PMS) system with two 6-inch balanced guns, processing thin films in areas as large as 450 cm2 grown on soda-lime glasses. Conducting glasses (SnO2 of 7 Ω/□) were also used only fo...

Photoluminescence spectra and their dependence on the temperature have been used to study the peculiarities of the red photoluminescence in low-dimensional Si structures, such as porous silicon and silicon oxide films with an admixture of silicon. It has been shown that red photoluminescence band of Si wires is complex and can be decomposed into tw...

Comparative investigations of the "red" band photoluminescence (PL) peculiarities of the porous silicon (P-Si) and silicon in silicon oxide films were carried out. The photoluminescence (PL) mechanism of these systems was determined using PL and Raman scattering spectroscopies, as well as atomic force microscopy (AFM). Overall, significant results...

A study of the electrical conductivity of polypyrrole-polyoxyphenylene composites (PPy-POP and PPy-POP-MPcTS) prepared by in situ electropolymerization is presented, where MPcTS stands for tetrasulfonated tetrasodium metallophthalocyanine salts and is used as a second dopand for polypyrrole. The conductivity is studied as a function of temperature...

We present in the results of this work, the influence of oxygen and the gradient of temperature in the processing of CdTe thin films, by using the close space vapor transport (CSVT) technique. In general the kinetic process is strongly influenced by these parameters; where a reduction in the growth rate, grain size; an increase in the intergrain ba...

The processing of large area thin films solar cells represents a challenge, mainly due to the need for optimal setting of the critical growth parameters for scaling-up of the processes that guarantee homogeneous properties in the sub-minimodule architecture. We have been working with a Radio-Frequency Planar Magnetron Sputtering (RF-PMS) system, pr...

We report in this work the results of the studies on the luminescent emission bands in policrystalline CdTe thin films at 10K, obtained by the use of luminescence excitation spectroscopy (LES) technique, in the range of exciting photon energies lower than the energy gap Eg (1.606 eV). We have been abled to detect a complex structure of the defect b...

The processing of large area thin films solar cells represents a challenge, mainly due to the optimal setting of the different critical growth parameters in this scaling-up process, than can guarantee a homogeneous-surface-photovoltaics response in the subminimodule architecture. We have been working with a radio-frequency planar magnetron sputteri...

We report the photoluminescence spectra of CdTe polycrystalline thin films at 10 K as a function of the exciting photon energy in the 1.59 to 1.71 eV range. Our results indicate that the ratio of the maximum intensity of the bound exciton band (Ib at ≈1.59 eV) to that of the defect band (Id at ≈>1.45 eV) shows resonances in this range. Above the ba...

A study of the optical and electrical properties of a conducting polypyrrole–polyoxyphenylene composite, PPy–POP, prepared by insitu electropolymerization is presented. Electropolymerization was performed potentiostatically in a solution of pH 9 which contained the monomers pyrrole, allylphenol and sodium 4-hydroxybenzenesulfonate (4HBS), by applyi...

A study of the in situ electrochemical preparation of conductive composite films of polypyrrole and non-conducting polyoxyphenylene is presented. Electropolymerizations of pyrrole were carried out in the presence of the phenolic monomers 2-allylphenol (2AP) and 4-hydroxybenzenesulfonic acid sodium salt (4HBS) in an aqueous alkaline solution (ph=9)...

A new gas sensor using a polypyrrole film grown on the surface of an interdigitated-capacitor substrate was proposed for the detection of carbon monoxide (CO). An experimental set-up was established and the properties of the sensor and the responses to different temperatures, gas flow rates, and CO concentration were measured and discussed. The max...

Semiconducting films of CdTe grown by close-spaced vapour transport (CSVT) were studied by photoluminescence. One luminescence band located around 1.588 eV and labelled as /BE was observed at a temperature of T=10 K. Such a band was studied over a wide range of temperatures (10-300 K), and the mechanisms involved in it were identified. Both band-to...

We report the first systematic measurements of the temperature dependence of the photoluminescence (PL) in the range of 10?300 K in CdTe. The experiments were carried out on semiconducting CdTe films of high quality grown by a modified close-spaced vapour transport (CSVT) technique. Several luminescence bands were observed, one around 1.4 eV showin...

In the present work we analyze the effect of nitrogen incorporation on the structural properties of hydrogenated amorphous carbon films. Photoluminescence, Raman and optical studies indicate that the high nitrogen content induces the formation of sixfold fused rings clusters (graphite layers).

Carbon films have been produced using a graphite hollow cathode and an r.f. plasma of hydrogen or hydrogen and argon. No hydrocarbon gas was used. The films were subjected to heat treatments up to 700 °C in air. The optical properties of the films were studied using Fourier transform IR, UV-visible, Raman, ellipsometry and photoluminescence techniq...