0000000000280625
AUTHOR
F. Fabreguette
Cathodoluminescence and structural studies of nitrided 3D gallium structures grown by MOCVD
Abstract Cathodoluminescence (CL) spectrum imaging and grazing incidence X-ray diffraction (GIXRD) are employed to investigate nitride three-dimensional (3D) gallium structures. The metallic precursors are naturally obtained on a large variety of substrates by metal-organic chemical vapor deposition (CVD) with different shape/size controlled by the growth conditions, especially the temperature. These 3D metallic structures are subsequently exposed to a nitridation process in a conventional CVD reactor to form GaN nanocrystals, as confirmed by GIXRD measurements. CL spectroscopy shows visible light emission (2.5–2.8 eV) excited from the GaN in the 3D structures.
Anisotropic and non-heterogeneous continuum percolation in titanium oxynitride thin columnar films
International audience; We report the percolation behaviour of the conductivity of titanium oxynitride films grown by low-pressure metal-organic chemical vapour deposition, composed of TiNxOy mixed with TiO2. The usual DC parameters (t, s and Φc), obtained from the effective media theory equations, are compared to the universal values (s = sun while t < tun because of the film anisotropy). This is the first example of an electrical continuum percolation applied to columnar films with chemically similar conducting and insulating units (non-heterogeneous percolation) whose mixing is based upon the growth temperature during the film growth.
Structural and in depth characterization of newly designed conducting/insulating TiN O /TiO2 multilayers obtained by one step LP-MOCVD growth
Abstract TiNxOy/TiO2 multilayers have been grown by LP-MOCVD using titanium isopropoxide (TIP) precursor during the whole growth, but with an ammonia flow interrupted for the TiO2 layers. The one step growth process used to grow these structures allowed to stack the conducting and insulating layers without any growth breakdown. SIMS and TEM analyses showed the presence of an alternated insulating/conducting layers structure. Moreover, electrical measurements allowed to measure the dielectric part of insulating TiO2 stacked in these structures, whose permittivity was found to be about 80 for a MOS structure. Thus, such multilayers may lead to very promising applications in the microelectroni…
X-ray multiple diffraction in the characterization of TiNO and TiO2 thin films grown on Si(001)
Abstract TiO 2 and TiN x O y thin films grown by low pressure metal-organic chemical vapor deposition (LP-MOCVD) on top of Si(0 0 1) substrate were characterized by X-ray multiple diffraction. X-ray reflectivity analysis of TiO 2 [1 1 0] and TiNO[1 0 0] polycrystalline layers allowed to determine the growth rate (−80 A/min) of TiO 2 and (−40 A/min) of TiNO films. X-ray multiple diffraction through the Renninger scans, i.e., ϕ -scans for (0 0 2)Si substrate primary reflection is used as a non-conventional method to obtain the substrate lattice parameter distortion due to the thin film conventional deposition, from where the information on film strain type is obtained.
Structural characterization of TiNxOy/TiO2 single crystalline and nanometric multilayers grown by LP-MOCVD on (110)TiO2
TiO2/TiNxOy superlattices were grown by Low Pressure-Metal-Organic Vapor Phase Epitaxy (LP-MOVPE) technique at deposition temperatures ranking from 650 to 750°C. The growth was performed on top of TiO2(110) rutile substrates. Intense peaks observed in the X-rays rocking curves and θ-2θ diffraction patterns show the presence of crystalline epilayers. The TiNxOy layers were grown in a (200) cubic structure on the (110) quadratic TiO2 epilayer structure. Transmission electron microscopy confirmed the XRD results and showed the formation of periodic and well structured epilayers.
Conductimetry and impedance spectroscopy study of low pressure metal organic chemical vapor deposition TiN O films as a function of the growth temperature: a percolation approach
Abstract Titanium oxinitride thin films have been grown by low pressure metal organic chemical vapor deposition (LP-MOCVD) using titanium isopropoxide, Ti(OCH(CH 3 ) 2 ) 4 (TIP) and NH 3 precursors in a growth temperature range from 450 to 750°C on sapphire substrates. The electrical behaviour of these films was studied between 400 and 173 K, revealing three different behaviours, ranking from a hopping conductivity (450–500°C) to a conducting one (700–750°C), with a dual behaviour for the intermediate growth temperatures. Moreover, at room temperature, both conductimetry and impedance spectroscopy highlighted a percolation behaviour, interpreted in terms of continuum percolation. The effect…
Structural characterization of TiO2/TiN O (δ-doping) heterostructures on (1 1 0)TiO2 substrates
Abstract TiO2/TiNxOy δ-doping structures were grown on the top of (1 1 0)TiO2 rutile substrates by low pressure metal-organic vapor phase epitaxy (LP-MOVPE) technique at 750 °C. The samples were analyzed by high resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS) and X-ray diffraction techniques (rocking curves and φ-scans). The presence of satellites in the (1 1 0)TiO2 rocking curve revealed the epitaxial growth of 10 period δ-doping structures. The thickness of the TiO2 layers, 84 nm, was deduced from the satellites period. HRTEM observations showed around 1.5 nm thick δ-doping layers, where the presence of nitrogen was detected by EELS. The analy…
Temperature and substrate influence on the structure of TiN O thin films grown by low pressure metal organic chemical vapour deposition
Abstract This paper presents the growth and characterization of titanium oxinitride (TiN x O y ) films grown by low pressure metal organic chemical vapour deposition (LP-MOCVD). The film nitrogen content, obtained by Rutherford backscattering spectroscopy (RBS), increases as the growth temperature increases (from 23 at.% at 450°C to 46 at.% at 750°C). Below 550°C, the films do not show any X-ray diffraction pattern. Above 550°C, the deposited films present the (111) and (200) TiN textures. Films deposited on (100) Si exhibit a 2 θ shift to higher Bragg angles, depending on the N/O ratio. These shifts are explained by using a substitutional oxygen model. Moreover, the atomic structure of suc…
MOCVD growth of TiO2 thin films on single crystal GaAs substrates
Abstract TiO 2 thin films have been grown on (100)GaAs and (111)GaAs substrates by low-pressure metal organic chemical vapour deposition (LP-MOCVD). Titanium(IV) isopropoxide, Ti{OCH(CH 3 ) 2 } 4 , was used as a precursor and TiO 2 films were obtained without an additional oxygen flux. Scanning electron microscopy (SEM) experiments have shown a well ordered rod-like crystallisation in the films grown on (100)GaAs. This ordered crystallisation was favoured by a high deposition temperature ( T d =700°C). By contrast, no distinct order was observed in the films grown on (111)GaAs substrates. X-ray diffraction patterns revealed a mainly rutile structure for the TiO 2 films deposited on (100)GaA…
Structure and properties of GaNxOy films grown by nitridation of GaAs (100) substrates
GaAs (100) substrates have been heat-treated in a metal-organic chemical vapor deposition reactor under flows of NH 3 and an oxygen organo-metallic precursor at temperatures between 650°C and 750°C. Yellowish films formed at the surface of all the samples. Gallium, nitrogen and oxygen were detected by EDX analysis of the films. The oxygen content was estimated in the range of at 5-10 at% depending on the heat-treatment temperature. X-ray diffraction and HRTEM results indicate that the structure of the films corresponds to the hexagonal wurtzite phase of GaN with an expanded unit cell. Raman spectra show hands corresponding to the Raman active GaN modes as well as disorder-activated broad ba…
Thermal effects on the growth by metal organic chemical vapour deposition of TiO2 thin films on (100) GaAs substrates
Abstract TiO 2 thin films were deposited on (100) GaAs substrates by LP-MOCVD with deposition temperatures ( T d ) ranking from 450 to 750 °C. The structure of these layers was studied by X-ray diffraction (XRD) and Raman spectroscopy. The growth of the TiO 2 anatase phase was observed for T d T d >600 °C. Finally, X-ray photoelectron spectrometry (XPS) and secondary ion mass spectroscopy (SIMS) experiments showed the presence of small quantities of Ga and As through the whole film thickness, slightly increasing at the surface of the layers. This result was related to the SEM observations and explained by considering the growth conditions.
Correlation Between the Electrical Properties and the Morphology of Low-Pressure MOCVD Titanium Oxynitride Thin Films Grown at Various Temperatures
Titanium oxynitride (TiN x O y ) thin films were deposited by low-pressure metal-organic CVD (LP-MOCVD) on (100) silicon, sapphire, and polycrystalline alumina substrates. Titanium isopropoxide (TIP) and ammonia were used as precursors. The influence of the growth temperature, ranking from 450°C to 750°C, was investigated by scanning electron microscopy (SEM), and electrical DC measurements. Rutherford back-scattering (RBS) measurements were used to determine the N/O ratio in the films. The surface observations of the deposited films showed two morphological transitions. The resistivity decreased with the growth temperature, while the nitrogen content increased. Moreover, for the highest de…
Amorphous TiO2 in LP-OMCVD TiNxOy thin films revealed by XPS
Abstract TiN(O)–TiO 2 thin films were prepared on Si(1 0 0) by the low pressure organo metallic chemical vapor deposition (LP-OMCVD) method, using ammonia and titanium isopropoxide as precursors. In order to complete previous characterizations, an Ar + bombardment/XPS coupled study was carried out. This method is based on the fact that the behavior of a compound towards an ion bombardment is a function of its composition. In particular, Ar + bombardment of TiO 2 (whatever its form) leads to a preferential sputtering of oxygen atoms with subsequent reduction of titanium and formation of Ti 3+ and Ti 2+ easily detectable by XPS from a significant broadening of the Ti 2p lines. In the opposite…