Ravi M. Todi

Comparison of the agglomeration behavior of thin metallic films on SiO2

The stability of continuous metallic thin films on insulating oxide surfaces is of interest to applications such as semiconductor interconnections and gate engineering. In this work, we report the study of the formation of voids and agglomeration of initially continuous Cu, Au, Ru and Pt thin films deposited on amorphous thermally grown SiO2 surfaces. Polycrystalline thin films having thicknesses in the range of 10–100nm were ultrahigh vacuum sputter deposited on thermally grown SiO2 surfaces. The films were annealed at temperatures in the range of 150–800°C in argon and argon+3% hydrogen gases. Scanning electron microscopy was used to investigate the agglomeration behavior, and transmission electron microscopy was used to characterize the microstructure of the as-deposited and annealed films. The agglomeration sequence in all of the films is found to follow a two step process of void nucleation and void growth. However, void growth in Au and Pt thin films is different from Cu and Ru thin films. Residual ...

Amorphous-SiCBN-Based Metal–Semiconductor–Metal Photodetector for High-Temperature Applications

A photodetector (PD) with metal-semiconductor-metal (MSM) structure has been developed using an amorphous SiCBN film. The amorphous SiCBN film was deposited on the silicon substrate using reactive RF magnetron sputtering. The optoelectronic performance of the SiCBN MSM devices has been examined through photocurrent measurements. Temperature effect, with respect to photocurrent ratios, has been studied. The detector sensitivity factor, which is determined through the PD current ratio, was greater than five at room temperature. Furthermore, the device showed an excellent current sensitivity factor that is greater than two even at a higher temperature of 200 oC . The improved performance of the device at higher temperatures could open avenues for high-temperature PD applications.

In Situ High Temperature Electrical Characterization of RF Sputtered SiCBN Thin Films

Electrical properties of reactively sputtered SiCBN thin films were studied at high temperature conditions. In situ electrical characterization was performed through sheet resistance measurements in the temperature range from room temperature to 900°C. The electrical properties were observed to be extremely sensitive with respect to variations in the chemical composition, and bonding structure of the SiCBN films. The film stoichiometry, obtained with no N 2 gas flow, showed very interesting electrical characteristics that have been correlated with the chemical structure of the material. Multiple heating and cooling cycles show uniquely stable resistance readings. This is presumed to be due to the formation of a stable surface passivation oxide layer leaving the bulk of the thin film unaffected. This was further confirmed through secondary ion mass spectroscopy depth profile. The thermal stability and stable reproducible electrical properties indicate potential for low cost high temperature thin film applications.

Effect of N2/Ar gas mixture composition on the chemistry of SiCBN thin films prepared by RF reactive sputtering

In this work we report the deposition and characterization of amorphous thin films of silicon boron carbon nitride (SiCBN). The SiCBN thin films were deposited in a radio frequency (rf) magnetron sputtering system using reactive cosputtering of silicon carbide (SiC) and boron nitride (BN) targets. Films of different compositions were deposited by varying the ratios of argon and nitrogen gas in the sputtering ambient. Surface characterization of the deposited films was performed using X-ray photoelectron spectroscopy and optical profilometry. Studies reveal that the chemical state of the films is highly sensitive to nitrogen flow ratios during sputtering. Surface analysis shows that smooth and uniform SiCBN films can be produced using this technique.

Multilevel sensitization of Er3+ in low-temperature-annealed silicon-rich SiO2

The dynamics of Er3+ excitation in low-temperature-annealed Si-rich SiO2 are studied. It is demonstrated that Si-excess-related indirect excitation is fast (transfer time τtr 2.3 μs. The fast and slow excitations of the I413/2 level account for an approximately equal fraction of the excitation events: 45%–50% and 50%–55%, respectively.

Observation of temperature-independent internal Er3+ relaxation efficiency in Si-rich SiO2 films

Time-dependent photoluminescence measurements of low-temperature-annealed Er-doped Si-rich SiO2 were conducted at sample temperatures 15–300 K. The erbium internal relaxation efficiency from the second (I411/2) to the first (I413/2) excited state upon luminescence-center-mediated Er3+ excitation is investigated. Despite the observation of temperature-dependent relaxation rates, the erbium internal relaxation efficiency is found to be remarkably temperature independent, which suggests that the internal relaxation efficiency is near unity. Internal relaxation is shown to account for 50%–55% of the I413/2 excitation events in the entire temperature range. These results demonstrate that high pump efficiency and stable operation of devices based on this material will be possible under varying thermal conditions.

X-Ray Photoelectron Spectroscopy Analysis of Oxygen Annealed Radio Frequency Sputter Deposited SiCN Thin Films

Thin films of amorphous silicon carbide nitride (a-SiC x N y ) were deposited in a rf magnetron sputtering system using a sintered SiC target. Films with various compositions were deposited onto silicon substrate by changing the N 2 /Ar gas ratios during sputtering. These films were annealed in dry oxygen ambient in the temperature range of 400-900°C. Subsequently these annealed films were characterized using X-ray photoelectron spectroscopy to investigate the chemical composition and oxidation kinetics at each annealing temperature. The results indicated that the oxidation of films was more gradual for the samples deposited with no nitrogen compared to the ones deposited with nitrogen.

Characterization of Pt-Ru binary alloy thin films for work function tuning

This letter describes materials and electrical characterization of Pt-Ru binary alloy metal gate electrodes for control of the electrode work function. The work function of the Pt-Ru binary alloy system can be tuned over a wide range of 4.8-5.2 eV. The results indicate that the change of film properties, i.e., resistivity, work function, and crystal structure, with composition is consistent with the equilibrium phase diagram and that the work function in the face-centered cubic and hexagonal close-packed single-phase regions is only weakly dependent on composition, whereas a strong dependence is observed in the intermediate compositional range.

Excitation wavelength independent sensitized Er3+ concentration in as-deposited and low temperature annealed Si-rich SiO2 films

Erbium sensitization is observed in as-deposited Er3+ doped Si-rich SiO2, ruling out the involvement of Si nanocrystals in the Er3+ excitation in these samples. The Er3+ excitation cross section in this material is similar within a factor 3 to that of samples annealed at 600 °C under 355 and 532 nm excitation. The density of sensitized Er3+ ions is shown to be excitation wavelength independent, while the shape of the Er3+ excitation spectra is governed by a wavelength dependent Er3+ excitation cross section. These findings enable the use of a broad range of wavelengths for the efficient excitation of this gain medium.

Comparison of the Work Function of Pt–Ru Binary Metal Alloys Extracted From MOS Capacitor and Schottky-Barrier-Diode Measurements

This paper describes a systematic comparison of work function for the Pt-Ru binary-alloy metals, extracted from capacitance-voltage (C-V) characteristics of MOS capacitors and the current-voltage (I-V) and C-V characteristics of Schottky-barrier diodes. Our results indicate that the work function of the Pt-Ru binary-alloy system can be tuned over the wide range of 4.8-5.2 eV. Furthermore, the results indicate that the change of film properties, i.e., resistivity, work function, and crystal structure, with composition is consistent with the equilibrium-phase diagram and that the work function in the face-centered cubic and the hexagonal-close-pack single-phase regions is only weakly dependent on composition while a strong dependence is observed in the intermediate compositional range. It is also observed that work-function values obtained from the Schottky I-V analysis are significantly lower than those extracted from the MOS C-V data