IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Core and valence level spectra of (Sm0.50Ca0.50)MnO3 are reported. The spectral weight of the valence band has a peak 6 eV below Fermi level. Comparative analysis with the similar class of compounds suggests that width of the valence band is low for this compound. Semiconductor type behaviour of this compound is qualitatively predicted using the features of valence band and core level spectra.

Department Of Physics

GENERAL

Materials Science and Engineering B: Solid-State Materials for Advanced Technology

Photoemission studies on (Sm0.50Ca0.50)MnO3

A far-IR reflectance spectrum of a disordered Ba(Zn1/3Ta2/3)O3 dielectric resonator has been studied. The spectrum was analyzed with the Generalized Oscillator model. The real part of the dielectric constant (εr) and loss tangent (tanδ) calculated from the parameters obtained from the fit is comparable to the values measured at microwave frequencies. The possible mode identification and their individual mode contribution to the real and imaginary parts of the complex dielectric constant are also analyzed.

Materials Research Bulletin

Far-IR reflectance study on B-site disordered Ba (Zn1/3Ta2/3)O3 dielectric resonator

The aim of this work is to understand the effect of the tilting of octahedra on polar phonon modes of lattice vibration, which contributes a major part to the dielectric polarization in the crystal. The tolerance factor, which is a measure of the packing of ions in the perovskite unit cell, determines the tilting of oxygen octahedra in the perovskite materials. In this work we have discussed the variation of polar phonon frequencies with respect to the tolerance factor in the composition (Ba(1-x)Srx)(Zn1/3Ta2/3)O3 with x = 0.0, 0.3, 0.5, 0.7, 1.0. The dielectric properties measured at the microwave frequency range are also highlighted to support the ideas proposed in this paper.

Physica B: Condensed Matter

Far-IR reflectance study on (Ba(1-x)Srx)(Zn1/3Ta2/3)O3 dielectric resonators as a function of tolerance factor

The application of microwave cavity perturbation technique for the study of transients in semiconductors is becoming popular due to its simplicity in measurement procedure and high sensitivity. The paper discusses the effects of quality factor, sample size, and coupling factor on the sensitivity of the measurement. Also, it deals with a measurement approach for the study of triplet state transitions and excited state studies in organic solvents. Finally, a comparison between the cavity perturbation technique and the currently used reflection technique is made. © 1998 American Institute of Physics.

Fulltext

Journal of Applied Physics

Sensitivity analysis of transient measurements using the microwave cavity perturbation technique

Microwave quality factor measurements for pure and mixed stages of graphite ferric chloride intercalation compounds have been carried out at X-band microwave frequency of 9.1582 GHz. The change in quality factor and hence the loss confirms the metallic nature of the graphite ferric chloride intercalation compounds that were studied. © 1997 Elsevier Science S.A.

Materials Science and Engineering B

Microwave studies on some low stage graphite ferric chloride intercalation compound

The decay time constants of the transient photo conductivity for six polycrystalline silicon wafers of different grain sizes are analyzed as a function of temperature (90 to 450 K). The photo conductivity decay is split into three components, namely, surface, shallow traps and deep traps in grain boundary, which are analyzed in terms of the effect of surface recombination velocity, changes in carrier mobility and grain boundaries. This is utilized to evaluate the temperature dependence of mobility and grain boundary potential in polysilicon samples. © Les Éditions de Physique 1996.

Journal de Physique III

Transient photo conductivity decay study on polycrystalline silicon

Microwave cavity perturbation technique has been employed for the study of photo conductive transients in semiconductors. A new approach of measuring the quality factor of the microwave cavity using cavity perturbation technique (reported in Rev. Sci. Instrum. 65 (1994) 453] is incorporated for this purpose. Measurements with this contactless technique on carrier lifetimes in various single and polysilicon and the analysis of the observed microwave transient photo conductivity decay with temperature is reported.

Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers

Study of microwave transient photo conductivity on single and polysilicon using cavity perturbation technique

Suitable correction factors are incorporated in the measurement of shift in resonance frequency and full width at half-maximum in the cavity perturbation technique when the sample is inserted partially into the cavity. The present approach is observed to be more accurate compared to the available theories and it does not have limitations concerning the shape of the sample. Several standard samples are taken for the present measurement and compared with the full insertion method. Some of the samples are partially inserted into the cavity step by step and the experimental results are compared with the present approach and that of Lehndroff. © 1996 American Institute of Physics.

Review of Scientific Instruments

Measurement of complex dielectric permittivity of partially inserted samples in a cavity perturbation technique

The cavity perturbation technique is employed for the characterisation of semiconductors at microwave frequency for its conductivity. Temperature variation of microwave conductivity studies provide the information regarding the band gap, scattering parameter and impurity ionization energy. Change in the real part of the dielectric permittivity with conductivity indicates the change in the momentum relaxation time. © 1995 the Indian Academy of Sciences.

Pramana

Microwave conductivity studies on some semiconductors

The transient nature of optical absorbance and the microwave cavity perturbation technique are used to measure the minority carrier lifetime in a polycrystalline thin film of Zn3P2 as well as to observe the spectral photoabsorbance. It has been observed that the transient decay curves consist of two components attributed to the surface carriers and the bulk carriers. The analysis of these spectral variation of carrier lifetime and spectral photoabsorbance indicate the possible band-band transitions in this material. © 1995.

Thin Solid Films

Minority carrier lifetime in thin films of Zn3P2 using microwave and optical transient measurements

A new approach of measuring the quality factor of the reflection type microwave cavity resonator for calculating the complex dielectric permittivity of solid and liquid samples in the cavity perturbation technique is proposed. This approach, based on the measurement of reflected power from the cavity at resonance, effectively reduces the measurement procedure and increases the accuracy. As the quality factor can be measured very fast using this approach, this approach can be extended to monitor the conductivity decay of the semiconductor samples.

New approach of measuring the Q factor of a microwave cavity using the cavity perturbation technique

A new technique, based on the cavity resonance, of measuring the complex dielectric permittivity of liquid samples is described in detail. The errors in the measurement of the real and imaginary parts of the complex dielectric permittivity are ∼±1% and ±3%, respectively. The complex dielectric permittivity values measured using this method for some standard liquids are also presented. A comparison is made between the present values and the values obtained using standard techniques.

A new technique of measuring the complex dielectric permittivity of liquids at microwave frequencies

The excess parameter studies in the microwave frequency region (X-band) on complex dielectric permittivity for the binary mixtures are reported. The methods employed are fixed cavity perturbation technique and adjustable plunger cavity technique. Also Gopalakrishna method is used to calculate the relaxation time of the polar solute in a non-polar solvent. The samples under study are acetonitrile, chlorobenzene, dimethyl formamide, carbon tetrachloride and benzene. © 1993 the Indian Academy of Sciences.