N. Nath

Thickness determination of ultrathin metal films using the X-ray fluorescence technique

Abstract The X-ray fluorescence technique was used to determine the thickness of single-layered, double-layered and triple-layered films of copper, bismuth and gold on mylar substrates. An annular 109 Cd X-ray source of 5 mCi was used to excite hte characteristic X-rays. The background was much lower as well as flat in the present study in comparison with our earlier results an 241 Am exciter source. This resulted in a downward extension of the lower limit of thickness measurement of thin films coupled with an improved accuracy.

Discrepancies in X-ray excitation efficiencies using a Si(Li) detector system

Abstract X-ray excitation efficiency measurement using a Si(Li) detector shows a decrease relative to the calculated values for higher Z. In the present analysis we study the contribution of the system geometry to the effective detector efficiency and hence to the observed values of the excitation efficiency.

Simple and inexpensive single-oscillation quartz crystal thin-film thickness monitor and growth-rate meter

Commercially available quartz crystal thin-film thickness monitors have limitations due to: (i) their inability to indicate the absolute frequency of oscillation of the mass measuring crystal; and (ii) the instability of the variable frequency LC oscillator, if any, incorporated in the circuit. Recently it has been suggested that it is economical and simple to use a digital frequency meter for the direct measurement of the frequency shift due to film deposition of the measuring crystal. Such an arrangement gives better results than commercial film thickness monitors. A single oscillation quartz crystal monitor and growth rate meter has been designed using this idea and locally available electronic components. In this instrument a quartz crystal wafer having one pair of gold electrodes is used, while the shift in resonance frequency measured by a digital frequency meter is used for the estimation of thickness of thin films. To measure the rate of growth of the film the resonance frequency signal from the crystal is suitably processed to produce a DC signal, which may be recorded on an x-y/x-t recorder to obtain the rate of growth during the deposition of the film.

Elemental analysis of polymetallic nodules from the Central Indian Basin : A study using EDXRF

Polymetallic nodule samples from the Central Indian Basin were analysed using energy-dispersive x-ray fluorescence employing the fundamental parameter approach. Photons of 5.96 and 22.6 keV, from radioactive sources of 55Fe and 109Cd, respectively, were used for exciting the samples. Fifteen elements, namely Si, Cl, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Sr, Y, Zr, Mo and Pb, were quantified. The samples were diluted in cellulose nitrate powder to reduce the enhancement and absorption effects due to the unknown matrix. The experimental procedures adopted for elemental analysis were checked by analysing a NIST certified reference material (SRM 2710) and a polymetallic nodule standard reference material (NIO-2388). The measured concentrations of various elements present in the nodule samples were compared with those reported earlier using ICP-AES and ICP-MS.

Thin film thickness monitoring using a doubly oscillating quartz crystal and measurement of growth rate

A single quartz crystal wafer of 5 MHz frequency and 20 mm*20 mm size, with two pairs of circular gold electrodes deposited on it, was used to measure the rate of growth and the thickness of thin films during deposition. This arrangement may be called a doubly oscillating quartz crystal monitor (DQM). The main limitations in the use of this arrangement arises from the coupling between the two electrode system. The coupling was minimised by depositing the gold electrodes at a suitable distance of about 4.2 mm. Further, the thin film whose thickness is to be measured was deposited on one side of one electrode pair while the other pair was kept covered from deposition. The resonance frequencies of the two electrode system were then processed in a conventional manner and the beat frequency was measured by a digital frequency meter. The latters output was analysed in a frequency-to-voltage converter and the resulting output voltage plotted on a X-Y recorder or X-t chart recorder was proportional to the rate of growth of thin films during deposition.

K and L shell X-ray relative intensity measurements

K shell X-ray intensity ratios (Kβ/Kα) were measured for elements of intermediate atomic number (20 ⩽Z⩽ 49). Photon excited characteristic X-rays from thin-film samples were detected using a high-resolution Si(Li) detector system. The X-ray intensities thus obtained were corrected for the detection efficiency of the system and self-absorption effects within the sample. The results obtained were in good agreement with theoretical values. Relative intensities for L3 sub-shell X-rays, i.e., Lα/Ll, are also reported for heavier atomic number elements at photon excitation energies correspoinding to Ag K X-rays.

Photon induced fluorescence cross-sections for K shell X-ray lines

X-ray fluorescence cross-sections for Kα lines have been calculated for K, Ca, Ti, V, Sr, Mo, Ag, In, Sb and Sn at two exciting energies, namely Mn K X-rays from 55Fe and 59.6 keV gamma rays from 241Am. Cross-sections have also been determined experimentally using a high-resolution Si(Li) detector system. Within experimental error, an agreement was obtained between the measured and the calculated values of the cross-sections.

Aluminized Mylar as Si(Li) detector window for x-ray fluorescence spectrometer

Abstract A thin (1–2 mil) Be foil is generally used as a window in a Si(Li) detector system. It was replaced by an aluminized Mylar foil (0.5 mg/cm2 thick aluminium of 99.999% purity coated on a 1 mil thick Mylar foil). The aluminized Mylar window is found to be a useful and simple substitute for the Be window.

Ion beam analysis of high temperature superconducting samples

Abstract Characterization of high temperature superconducting film and bulk samples has been carried out using 2 MeV α-particle Rutherford backscattering, 2.4 MeV proton elastic scattering, 2.4 MeV proton-induced x-ray emission, 9 MeV proton induced γ-ray emission and 100 MeV iodine elastic recoil detection analysis techniques. The objective was to compare different ion beam based techniques for: (i) compositional analysis; and (ii) consistency of the results obtained for samples prepared using similar preparation methodology.

Effect of post-deposition aging on thin indium films

Abstract The effect of post-deposition aging on vacuum-deposited thin indium films was studied. Low and high resistivity films of thicknesses about 1000 A and less than 50 A respectively were deposited onto Corning 7059 glass substrates. The electrical resistance of the low resistivity films was found to decay asymptotically with time just after deposition. However, the reverse trend was observed for high resistivity films. Similar behaviour has also been reported by other workers for thin gold films.