A. Bensaoula

Formation of carbon nitride films on Si(100) substrates by electron cyclotron resonance plasma assisted vapor deposition

We report the growth of thin carbon nitride films on Si(100) substrates at temperatures in the range of 100–700 °C using electron‐beam evaporation of graphite assisted with electron cyclotron resonance (ECR) plasma generated nitrogen species. The effect of the substrate temperature, and the nitrogen flow on the composition ratio C/N, and the C—N bonding were investigated using Fourier transform infrared spectroscopy (FTIR), x‐ray photoelectron spectroscopy (XPS), Rutherford backscattering spectroscopy (RBS), and Raman spectroscopy. The FTIR spectra show that the films produced exhibit a very high visible to infrared transmittance (0.85–0.95). These spectra were dominated by amine group (NH2) with the presence of C‐N stretching modes. From both RBS and XPS, the nitrogen concentration in the film was calculated and was found in the range of 24%–48%, depending on the nitrogen partial pressure in the ECR source. Raman spectrum of the high nitrogen content thin film shows a well resolved peak at 1275 cm−1 sugg...

Visible emission from AlN doped with Eu and Tb ions

We report the observation of visible cathodoluminescence (CL) from AlN thin films grown on sapphire (0001) substrate by molecular beam epitaxy and doped by implantation with Eu3+ and Tb3+ ions. The strongest rare earth (RE) CL was observed from samples annealed at 1100 °C for 0.5 h in N2 ambient. The sharp characteristic emission lines corresponding to Eu3+ and Tb3+ intra-4fn shell transitions are resolved in the spectral range from 350 to 900 nm. The CL spectra were recorded over 1–16 keV electron energy in the temperature range of 8–330 K. The depth resolved CL spectral analysis gives the luminescence surface a dead layer thickness of ∼16 nm for implanted AlN samples. We observed several different recombination centers luminescing in the 286–480 nm spectral region due to the presence of structural defects and oxygen impurities. The time resolved spectra and the CL kinetics were studied. The decay times for 5D0→7F2 (Eu3+), 5D3→7F5 (Tb3+), and 5D4→7F6 (Tb3+) transitions at 300 K are ∼0.4, ∼0.9, and ∼0.4 m...

Physical properties of thin carbon nitride films deposited by electron cyclotron resonance assisted vapor deposition

Electron cyclotron resonance (ECR) plasma‐assisted vapor deposition has been used to grow thin carbon nitride films on Si(100) and sapphire substrates. The composition, structure, and optical properties of the films were investigated by x‐ray photoelectron spectroscopy (XPS), Rutherford backscattering (RBS), Raman, and optical absorption spectroscopies. The effect of varying the nitrogen gas flow, at constant substrate temperature and carbon deposition rate, on the C/N composition ratio and the CxNy crystal structure was investigated. From both RBS and XPS, the nitrogen concentration in the film was found to be in the range of 20%–48% and varied directly with the nitrogen partial pressure in the ECR source. In CN films with low nitrogen content, the Raman spectra showed no evidence of CN bonding and were characteristic of graphitic carbon. In contrast, the Raman spectra of high nitrogen content thin films show a wide peak at 1291 cm−1, suggesting the formation of a CxNy phase with predominately sp3 bondin...

Electrical properties of boron nitride thin films grown by neutralized nitrogen ion assisted vapor deposition

Boron nitride (BN) thin films (containing mixed cBN/hBN phase) have been deposited on Si(100) substrates using neutralized nitrogen beam and electron beam evaporation of boron. All as‐deposited BN films were p type with a room‐temperature carrier concentration in the range of 5×1016 to 1×1017 cm−3. The Mg‐doped BN films showed carrier concentrations in the range of 1.2×1018 cm−3 to 5.2×1018 cm−3 when the Mg cell temperature was varied from 250 to 500 °C. The films were analyzed for both majority elements (B and N) and dopant/impurity (Si, Mg, Fe, etc.) incorporation using secondary ion mass spectroscopy and mass spectroscopy of recoiled ions (MRSI). MRSI is shown to be superior for dopant characterization of boron nitride thin films.

Field emission properties of GaN films on Si(111)

GaN thin films were grown by electron cyclotron resonance molecular beam epitaxy on Si(111) wafers. X-ray diffraction and transmission electron microscopy revealed that the thin films were single crystals with a hexagonal symmetry and a clear textured structure. The average column size was determined to be close to 100 nm in diameter. Despite the large defect density, a strong room temperature photoluminescence signal with a full width at half maximum of 138 meV was observed from these samples. The surface exhibited random array of sharp tips at the microscopic level with about 5×109 tips/cm2 density. The field emission characteristics of the as-grown thin films were measured, and a threshold electric field as low as 30–40 V/μm and an emission current density of more than 100 mA/cm2 were obtained.

Growth of cubic boron nitride on Si(100) by neutralized nitrogen ion bombardment

Highly cubic phase and stoichiometric boron nitride films were deposited on Si(100) substrates using a neutralized nitrogen beam and electron beam evaporation of boron. High intensity, focused, and low‐energy neutralized nitrogen beam was supplied using a newly developed neutralizer atomic beam ion source (NABS) adapted to a Kaufman‐type ion source. The films were grown at substrate temperatures in the range 400–500 °C and a boron evaporation rate of 0.2 A/s. Infrared transmittance spectra of the films showed that a highly cubic phase (80%) was obtained in the area of the focused beam. These films were compared to those obtained using similar conditions but with the NABS disconnected from the ion source, and it was found that the cubic phase content decreases drastically (10%). The results show that the NABS was the determining factor in enhancing the formation of the cubic boron nitride films. Furthermore, the addition of Ar to N, which is reported to increase the momentum transfer and promote the format...

Growth of InAs/InP and InAsP/InP heterostructures by chemical beam epitaxy

Abstract We report for the first time that high quality pseudomorphically strained InAs 1- x P x /InP and InAs/InP (3% lattice mismatch) superlattices (SL) and strained multi-quantum wells (SMQWs) can be grown by chemical beam epitaxy (CBE). Structural properties and interface sharpness are investigated as a function of growth temperature within a range of 420 to 540°C. Interface sharpness, determined through the high resolution X-ray diffraction analysis of thin (1–5 monolayers) InAs single and multi-quantum well structures, is found to be better than 1 monolayer over a wide range of growth temperatures (450–490°C) and high quality SMQWs and SLs were achieved. Moreover, no temperature dependent variation of thicknesses (growth rates) was observed within the 440–500°C temperature range. The As versus P incorporation ratios in ternary InAsP/InP layers were also studied, showing that CBE is perfectly suited for a successful control of As composition in such heterostructures. Finally, the structural and optical properties of grown heterostructures, as studied with high resolution X-ray diffraction, RHEED and low temperatures photoluminescence analysis, indicate that pseudomorphic InAsP/InP and InAs/InP SMQWs are compatible with long wavelength (1 to 2 μm) opto-electronic applications.

Etching of tungsten with XeF2: An x‐ray photoelectron spectroscopy study

In situ x‐ray photoelectron spectroscopy measurements of both W(100) crystals and sputter‐deposited tungsten films exposed to a molecular beam of XeF2 with and without an accompanying argon ion beam have yielded the fluorine coverage and the chemical states of the adsorbed fluorine as a function of temperature, exposure, and ion dose. WF, WF2, WF3, and WF4 were found to exist on the tungsten surfaces. Room and elevated temperature exposures of clean tungsten resulted in the surface population of mainly WF species with WF4 observed on nonannealed samples. Ion dose promoted the formation of higher fluorine coordination species from the WF leading to the formation of volatile WF6 and thus resulting in ion‐enhanced etching of tungsten.

The temperature dependent variation of bulk and surface composition of InxGa1−xAs on GaAs grown by chemical beam epitaxy studied by RHEED, X-ray diffraction and XPS

The bulk as well as near-surface composition of InxGa1−xAs epilayers on GaAs grown by chemical beam epitaxy (CBE) has been investigated as a function of triethylindium (TEIn) flow rate and substrate temperature by reflection high energy electron diffraction (RHEED), X-ray diffraction, and X-ray photo electron spectroscopy (XPS). To clarify whether the bulk stoichiometry of CBE-grown ternaries can be extracted from the growth rate change as determined by the change in the period of RHEED oscillations from binary to ternary compound growth, a systematic study of growth rate change as a function of ternary bulk composition determined by X-ray diffraction has been performed at various temperatures. Our results show that for low growth temperatures there is a linear relationship between the two methods of determination, whereas no correlation is found for higher growth temperatures, in contrast to the MBE case where the two methods of determination give identical results. In the near surface region the epilayer composition is determined in situ by XPS. Using a new method for analysis of XPS spectra, where the inelastically scattered electrons are taken into account, an extraction of quantitative depth information on the upper monolayers is possible. Our results show that In surface segregation is of minor importance at 470°C, but surface segregation of In occurs in InxGa1−xAs at growth temperatures from 550 to 600°C. For samples grown at 550 and 600°C the surface In enrichment is not restricted to the upper monolayers, but extends to a depth ⩾ 50–75 .

Surface composition of BN, CN, and BCN thin films

Boron nitride (BN), carbon nitride (CN), and boron carbon nitride (BCN) thin films were deposited on sapphire and silicon using ion beam and electron cyclotron resonance plasma assisted physical vapor deposition. In situ Auger electron spectroscopy was used to investigate the effect of different growth parameters and postgrowth processing on the thin film surface composition. The bulk composition was determined by electron energy loss spectroscopy and electron microprobe analysis. Both BN and CN films show thermal stability up to 900 and 700 °C, respectively. Low growth temperatures favor nitrogen incorporation in CN films and the optimum temperature for quasistoichiometric BN is between 450 and 600 °C, depending on the nitrogen sources.