H. Riascos

DETERMINATION OF PHYSICAL RESPONSE IN (Mo/AlN) SAW DEVICES

This paper describes the experimental conditions in surface acoustic wave (SAW) designed on aluminum nitride (AlN) films grown on Si3N4 substrates by using pulsed laser deposition. Moreover it was studied the dependency of optical properties with temperature of deposition. The thickness, measured by profilometry technology, was 150 nm for all films. Moreover, SAW devices with a Mo/AlN/Si3N4 configuration were fabricated employing AlN buffer and Mo Channel. The morphology and composition of the films were studied using atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy analysis (XPS), respectively. The optical reflectance spectra and color coordinates of the films were obtained by optical spectral reflectometry technique in the range of 400–900 cm-1. In this work, a clear dependence in morphological properties, optical properties, frequency response and acoustic wave velocity as function of applied deposition temperature was found. It was also observed a reduction in reflectance of about 10% and an increase of acoustic wave velocity of about 1.2% when the temperature was increased from 200°C to 630°C.

OPTICAL PROPERTIES DEPENDENCE WITH GAS PRESSURE IN AlN FILMS DEPOSITED BY PULSED LASER ABLATION

AlN films were deposited by pulsed laser deposition technique (PLD) using an Nd: YAG laser (λ = 1064 nm). The films were deposited in a nitrogen atmosphere as working gas; the target was an aluminum high purity (99.99%). The films were deposited with a laser fluence of 7 J/cm2 for 10 minutes on silicon (100) substrates. The substrate temperature was 300 °C and the working pressure was varied from 3 mtorr to 11 mtorr. The thickness measured by profilometer was 150 nm for all films. The crystallinity was observed via XRD pattern, the morphology and composition of the films were studied using scanning electron microscopy (SEM) and Energy Dispersive X-ray analysis (EDX), respectively. The optical reflectance spectra and color coordinates of the films were obtained by optical spectral reflectometry technique in the range of 400 cm-1- 900 cm-1 by an Ocean Optics 2000 spectrophotometer. In this work, a clear dependence of the reflectance, dominant wavelength and color purity was found in terms of the applied pressure to the AlN films. A reduction in reflectance of about 55% when the pressure was increased from 3 mtorr to 11 mtorr was observed. This paper deals with the formation of AlN thin films as promising materials for the integration of SAW devices on Si substrates due to their good piezoelectric properties and the possibility of deposition at low temperature compatible with the manufacturing of Si integrated circuits.

Optical spectroscopy of emission from CN plasma formed by laser ablation

The characterization of a plasma plume is a key issue in laser ablation and deposition studies. The formation, composition and propagation of laser-produced plasmas used for pulsed laser deposition (PLD) of CN have been studied under film growth conditions. The plume was generated by focusing 1064 nm, 9 ns pulses from Nd:YAG laser on carbon target under nitrogen ambient. We investigated the different species, such as CII, CI, C2, NII and CN, in laser ablated CN plasma using optical emission spectroscopy. The spectral characteristics of the plasmas were measured to determine the plasma properties as gas pressure was changed from 10-5 to 90 mTorr. The intensities of molecular species did not depend on gas ambient whereas ion intensities did. The vibrational temperature shows dependence with gas pressure.

Spectroscopic study of emission coal mineral plasma produced by laser ablation

Spectroscopic analysis of plasma produced by laser ablation of coal samples using 1064 nm radiation pulses from a Q-switched Nd:YAG on different target under air ambient, was performed. The emission of molecular band systems such as C2 Swan System (d 3 Πg→a 3 Πu), the First Negative System N2 (Band head at 501,53 nm) and emission lines of the C I, C II, were investigated using the optical emission spectroscopy technique. The C2 molecular spectra (Swan band) were analyzed to determine vibrational temperature (0,62 eV); the density and electron temperature of the plasma have been evaluated using Stark broadening and the intensity of the nitrogen emission lines N II, the found values of 1,2 eV and 2,2 ×10 18

Optical emission spectroscopy of Aluminum Nitride thin films deposited by Pulsed Laser Deposition

In this work we study the Aluminium Nitride plasma produced by Nd:YAG pulsed laser, (λ = 1064 nm, 500 mJ, τ = 9 ns) with repletion rate of 10 Hz. The laser interaction on Al target (99.99%) under nitrogen gas atmosphere generate a plasma which is produced at room temperature; with variation in the pressure work from 0.53 Pa to 0.66 Pa matching with a applied laser fluence of 7 J/cm 2 .The films thickness measured by profilometer was 150 nm. The plasma generated was at different pressures was characterized by Optical Emission Spectroscopy (EOS). From emission spectra obtained ionic and atomic species were observed. The plume electronic temperature has been determined by assuming a local thermodynamic equilibrium of the emitting species. Finally the electronic temperature was calculated with Boltzmann plot from relative intensities of spectral lines. .