Thick Titanium Films Research Articles

Nanometer – Thick titanium film as a silicon migration barrier

Diffusion of silicon atoms to the topmost film surface poses significant challenges in various technological applications. In an effort to address this issue, titanium films with varying thicknesses were deposited on a silicon substrate to evaluate the efficacy of a thin titanium barrier film in blocking silicon migration to the upper film surface. Subsequently, the films were subjected to a 1-hour heating process in air at an oxidizing temperature of 430 K. Atomic force microscopy and Raman spectroscopy were employed to characterize the morphological and structural changes among the investigated films. X-ray photoelectron spectroscopy was utilized to explore variations in chemical composition, determine oxidation states, and measure the thicknesses of the thin titanium oxide layers. The findings revealed that titanium films with a thickness < 50 nm experienced silicon diffusion to their upper film surface. Moreover, an increase in the thickness of the oxide layers over the titanium film on the silicon substrate significantly reduced the migration of silicon to the titanium film surface. At 430 K, the study found that oxide layers at least 6.87 nm thick formed on a 35-nm thick titanium layer, which together successfully prevented silicon migration to the top surface of the film.

Electrical Conductivity and Optical Properties of Nanoscale Titanium Films on Sapphire for Localized Plasmon Resonance-Based Sensors

The developing area of plasmonics has led to the possibility of creating a new type of high-speed, high-sensitivity optical sensor for biological environment analysis. The functional layer of such biosensors are nanoscale films of noble metals. In this work we suggest using a thin film of titanium as a functional layer. This paper presents the results of the research on electrical and optical characteristics of 5 to 80 nm thick titanium films deposited on sapphire substrates by magnetron sputtering. It is shown that surface plasmon resonance is consistently observed in the investigated titanium films and the theoretical grounds of surface plasmon resonance excitement is given. In structures with titanium films less than 15 nm thick, local plasmon resonance is observed along with surface plasmon resonance. Local plasmon resonance is more sensitive to the surface state of a thin film of titanium, which on the one hand increases the sensitivity of a biosensor, and on the other hand imposes restrictions on the parameters of nanoscale films.

Anodic formation of highly ordered TiO2 nanotube arrays on conducting glass substrate: Effect of titanium film thickness

Highly ordered TiO2 nanotube arrays were successfully fabricated using ammonium fluoride electrolyte by galvanostatic anodization technique. The nanotube arrays were grown perpendicular to the titanium film deposited onto conducting glass substrate. The effect of the different titanium film thicknesses on the morphology, optical, and electrical properties of TiO2 nanotube arrays is investigated. It is found that the titanium film thickness is a crucial parameter for achieving highly ordered TiO2 nanotube arrays. Morphological investigations on the nanotube arrays reveal that anodization of 1.5 μm thick titanium films leads to formation of pores at the upper layer of the film with nonuniform pore size distribution and poor interconnectivity. Instead, anodization of 2.5 and 2.0 μm thick titanium films with the same conditions leads to formation of highly ordered TiO2 nanotube arrays with uniform size and sharp clear tubular structures, which are well connected to each other. The absorbance and optical band gap of the TiO2 nanotube arrays are also inferred from the diffuse reflectance spectra.Highly ordered TiO2 nanotube arrays were successfully fabricated using ammonium fluoride electrolyte by galvanostatic anodization technique. The nanotube arrays were grown perpendicular to the titanium film deposited onto conducting glass substrate. The effect of the different titanium film thicknesses on the morphology, optical, and electrical properties of TiO2 nanotube arrays is investigated. It is found that the titanium film thickness is a crucial parameter for achieving highly ordered TiO2 nanotube arrays. Morphological investigations on the nanotube arrays reveal that anodization of 1.5 μm thick titanium films leads to formation of pores at the upper layer of the film with nonuniform pore size distribution and poor interconnectivity. Instead, anodization of 2.5 and 2.0 μm thick titanium films with the same conditions leads to formation of highly ordered TiO2 nanotube arrays with uniform size and sharp clear tubular structures, which are well connected to each other. The absorbance and optical band ...

Application of clean laser transfer for porphyrin micropatterning

Blister-based laser-induced forward transfer is proposed as a promising tool for clean, cold and liquid-free local transfer of various organic substances. The feature of the given technique is non-destructive local deformation of an absorbing metal film on a transparent support avoiding the metal sputtering. Application of the blister-based laser transfer of a Langmuir film to fabricate mesotetraphenylporphyrin micropatterns on a silica substrate has been demonstrated. The metal film thickness is found to be a key parameter, which determines the laser fluence range allowing the clean transfer, predominant mechanism of the blister formation and laser-induced heating of the transferred material. According to the numerical modelling confirmed by UV–vis absorption spectroscopy, the target with 1.5 μm thick titanium film provides negligible heating of the porphyrin transferred by 5 ns laser pulses.

Dye-sensitization of self-assembled titania nanotubes prepared by galvanostatic anodizationof Ti sputtered on conductive glass

Self-organized porous TiO2 nanotubes (NTs) were prepared on conductive glass by galvanostatic anodizing of sputtered titaniumin an NH4F /glycerol electrolyte. DC magnetron sputtering at an elevated substrate temperature (500 °C) was used to deposit 650 nm thick titanium films. After anodizing, NTs, 830 nm long, withan average external diameter of 92 nm, were grown; this gave a high conversion rate ofoxide from titanium (1.9), with a 220 nm thick layer of titanium, which was notoxidized, located at the base of the tubes. The NTs revealed a mainly amorphousstructure, which transformed mostly to anatase upon thermal treatment in air at450 °C.The tubes were sensitized by the N719 complex and the resultant photoelectrodes were incorporatedinto liquid dye solar cells (DSCs) and further tested under back-side illumination. High values ofVoc (714 mV) were obtained under 1 sun (AM 1.5), assigned to low dark current magnitude andlarge recombination resistance and electron lifetime. In addition, typical values of fillfactors (of the order of 0.62) were attained, in agreement with the estimated ohmicresistance of the cells in combination with low electron transfer resistance at theplatinum/electrolyte interface. The overall moderate power conversion efficiency(of the order of 0.3%) was mainly due to the low short-circuit photocurrents (Jsc = 0.68 mA cm−2),which was confirmed further by the corresponding IPCE values (5.2% at 510 nm). The magnitudeof Jsc was attributed to absorbed light losses due to back-side illumination of the cells, the low dye loading(due to the limited thickness of anodic titania) and the high charge transfer resistance at theTiO2 /conductive substrate due to the presence of barrier layer(s) underneath the tubes.These preliminary results encourage the DSC community to explore further thegalvanostatic anodizing of titanium in order to produce highly efficient porousTiO2 NTs directly on conductive glass. Current work is focusing on achieving complete anodizingof the metal substrate and full transparency for the photoelectrode in order to increase andoptimize the resultant cell efficiencies.

The tribological characteristics of titanium nitride coatings. Part I. Coating thickness effects

The tribological behavior of specimens coated by two layers, titanium nitride film as the top layer and titanium film as the underlayer, is studied. The coating layers of the bottom specimens were deposited using the cathodic arc ion plating process technique. Experiments were carried out on a wear test machine using a thrust-washer adapter to simulate the surface contacts between the steel ring (the upper specimen) and the titanium nitride coated washer (the bottom specimen). We address the subject about the influence of the thickness of the two coating layers on tribological behavior, wear mechanism, specimen's hardness and adhesive strength. A thin titanium nitride film in combination with a thick titanium film attenuates the adhesive strength, resulting in a significant increase in wear rate. The influence of the titanium nitride or titanium thickness on the friction coefficient is quite limited at higher sliding speeds. The specimen's hardness is increased by thickening the titanium nitride layer, but is lowered by increasing the titanium thickness. When the specimen's sliding speed is increased, both the wear rates and the friction coefficients show significant decline.

Ultra-high vacuum measurements of the internal stress of PVD titanium films as a function of thickness and its dependence on substrate temperature

The internal stress of thin titanium films was measured during, as well as after, their deposition under ultra-high vacuum (uhv) conditions using a cantilever beam technique. Diverse measurements were made at a number of constant deposition temperatures between room temperature and 350°C. At room temperature titanium films exhibit only tensile stress over the whole thickness range. In terms of our model for the origin of internal film stress such a stress curve is characteristic of materials with a low mobility, i.e. high melting point, and indicates columnar grain growth. For deposition at substrate temperatures above about 60°C, tensile, as well as compressive stresses are found with increasing film thickness. This indicates a transition to an island growth mode due to increased metal mobility. In addition, this increased mobility at a higher temperature leads to a more pronounced recrystallization which correlates well with the larger stress changes after the film deposition. Furthermore, results of experiments are presented in which we have used 100 nm thick titanium films as substrates for the deposition of a second titanium film. Variations in the chemical or physical properties (e.g. deposition temperature or oxidation) of this titanium substrate are also reflected in the stress vs thickness curves obtained for the additional titanium films.

Microstructure and Kinetics of the Interface Reaction Between Titanium Thin Films and (112) Sapphire Substrates

AbstractWe studied the reactivity of titanium with the R-plane (112) surface of sapphire by transmission electron microscopy (TEM), x-ray diffraction (XRD), and Rutherford backscattering (RBS) techniques. Cross-section TEM specimens were prepared from 200–400 nm thick titanium films deposited on sapphire at 25, 525, 554, 562, 580, 630, and 663°C to observe the interfacial region. In samples deposited at 25°C, without further annealing, no reaction zone could be seen in the TEM. In all other samples titanium reduced the sapphire to form Ti0 6 7[O0 3 3] and Ti3Al[O], Ti and Ti3Al with oxygen in solid solution. An activation energy of 24.7 ± 6 kcal/deg-mole was determined for the growth of the Ti3Al[O] layer. Layer thickness measurements from the TEM and RBS studies were within 10–20% of one another.

Constant-width variable-index transition for efficient Ti:LiNbO3waveguide-fiber coupling

A novel constant-width variable-index transition has been developed that allows for both low-loss fiber-waveguide coupling and efficient device operation on the same lithium niobate chip. A thick titanium film (750 Å) is utilized at the input end of the transition, resulting in large <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\Deltan</tex> and tight mode confinement. At the output of the transition, the waveguide is designed to be close to cutoff by decreasing the Ti thickness to 375 Å. This causes the mode size to increase so that mode coupling loss between a small mode-size waveguide ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/e</tex> intensity full width of 4.25 μm by full depth of 2.80 μm) and a single-mode fiber ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/e</tex> intensity full width of 7 μm) is reduced by approximately 1.4 dB per interface at 1.3-μm wavelength.

Processing of titanium films on silicon using a Q-switched ruby laser

A Q-switched ruby laser (with variable energy density up to 2.0 J cm −2 was used to process titanium films of thicknesses 300, 500 and 1000 Å deposited onto (100) single-crystal silicon substrates. Complete intermixing of titanium with silicon was observed for 300 Å films, while 500 and 1000 Å films were only partially reacted after multiple irradiations. A model based on diffusion of titanium in the liquid phase is proposed to explain the evolution of the distribution of titanium after successive laser irradiations.