Feby Jose

Response of magnetron sputtered AlN films to controlled atmosphere annealing

The present investigation deals with the examination of the response of amorphous AlN films to post-deposition annealing environments such as high vacuum (HV) and nitrogen atmosphere (NA). The c/a ratio values from GIXRD for both cases are around 1.602. The XPS profile of NA-AlN shows a deficiency of nitrogen on the surface, whereas the oxygen impurity level is negligible in the case of NA compared with HV. The PL spectra substantiate the nitrogen vacancies in NA-AlN. The amorphous AlN exhibits a nanoindentation hardness of 18 GPa.

Investigation of temperature dependent dielectric constant of a sputtered TiN thin film by spectroscopic ellipsometry

The temperature dependence of optical constants of titanium nitride thin film is investigated using Spectroscopic Ellipsometry (SE) between 1.4 and 5 eV in the temperature range of 300 K to 650 K in steps of 50 K. The real and imaginary parts of the dielectric functions e1(E) and e2(E) marginally increase with increase in temperature. A Drude Lorentz dielectric analysis based on free electron and oscillator model are carried out to describe the temperature behavior. With increase in temperature, the unscreened plasma frequency and broadening marginally decreased and increased, respectively. The parameters of the Lorentz oscillator model also showed that the relaxation time decreased with temperature while the oscillator energies increased. This study shows that owing to the marginal change in the refractive index with temperature, titanium nitride can be employed for surface plasmon sensor applications even in environments where rise in temperature is imminent.

Nanomechanical and optical properties of highly a-axis oriented AlN films

This paper reports optical and nanomechanical properties of predominantly a-axis oriented AlN thin films. These films were deposited by reactive DC magnetron sputtering technique at an optimal target to substrate distance of 180 mm. X-ray rocking curve (FWHM = 52 arcsec) studies confirmed the preferred orientation. Spectroscopic ellipsometry revealed a refractive index of 1.93 at a wavelength of 546 nm. The hardness and elastic modulus of these films were 17 and 190 GPa, respectively, which are much higher than those reported earlier can be useful for piezoelectric films in bulk acoustic wave resonators

Preferentially oriented electron beam deposited TiN thin films using focused jet of nitrogen gas

A modified electron beam evaporator has been used to synthesise TiN thin films with (111) preferred orientation. This new design involved in creating local plasma by accelerating the secondary electrons emitted from the evaporating ingot by a positively biased semi-cylindrical anode plate (biased activated reactive evaporation). To accelerate the reaction to form TiN, a jet of gas has been focused towards the substrate as a reactive gas. We have observed a preferred orientation (111) with to the surface normal in pole figure analysis. The residual stress by the classical sin technique did not yield any tangible result due to the preferred orientation. The hardness and modulus measured by nanoindentation technique was around 19.5 and 214 GPa. The continuous multicycle indentation test on these films exhibited a stress relaxation.

Phase selective gas sensing properties of nanostructured TiO 2 thin films

TiO2 thin films were prepared by r.f. magnetron sputtering and spray pyrolysis. Films were grown on Si (100) and interdigitated gold on alumina substrates. The film morphology and roughness were determined using atomic force microscopy. The films obtained by r.f. sputtering were smoother with rms surface roughness of about 0.8 nm (over a 5µm × 5 µm scan area) whereas the rms roughness of the films prepared by spray pyrolysis was around 3.9 nm (over 5 µm × 5 µm scan area). The crystal structure was determined using glancing incidence x-ray diffraction and it was observed that the r.f. sputtered films consisted of rutile phase while the films obtained by spray pyrolysis were anatase phase. The optical parameters namely, refractive index (n) and extinction coefficient (k) were estimated using a variable angle spectroscopic ellipsometry. Gas sensing studies with ammonia revealed that rutile phase is sensitive while the anatase phase showed no response. A correlation is given between optical, sensing properties and microstructure.

Nano‐Mechanical Property Studies of Ti1−xAlxN Thin Films

Titanium Aluminum Nitride (Ti1−xAlxN) thin films with different Al concentrations (64 & 81%) were deposited on SS substrate by reactive magnetron co–sputtering. GIXRD result shows that it has NaCl type crystal structure. Adhesion strength of Ti1−xAlxN with 81% Al (3 N) is higher than the 64% (1.4 N) because it is softer than the later. The average surface hardness of these films was measured as 34 and 30 GPa, respectively.