Raman spectroscopy on amorphous carbon films

Schwan, J.; Ulrich, S.; Batori, V.; Ehrhardt, H.; Silva, S. R. P.

doi:doi:10.1063/1.362745

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Determination of molecular orientation of very thin rubbed and unrubbed polyimide films

To determine the molecular orientation of rubbed and unrubbed poly[4,4′‐oxydiphenylene‐ pyromellitimide] (PMDA‐ODA) films, we have measured the infrared (IR) absorption spectra of PMDA‐ODA films on Si substrates as a function of the incident angle. The molecular orientation was determined by fitting the incident angle dependence and the IR dichroic ratio with the theoretical curves. The IR absorption was calculated by a transfer matrix method to take account of the multiple reflection and refrac...

Reabsorption, band‐gap narrowing, and the reconciliation of photoluminescence spectra with electrical measurements for epitaxial n‐InP

The effects of reabsorption and band‐gap narrowing (BGN) on experimental photoluminescence (PL) spectra of n‐InP grown by metalorganic chemical vapor deposition are analyzed. PL spectra show a pronounced widening of the main PL peak and a shift of that peak to higher photon energy with increasing doping due to band filling. However, the magnitude of these effects, both here and in earlier studies of n‐type III–V semiconductors, is smaller than expected based upon band filling calculations and el...

The origin and interpretation of the Raman features of amorphous (hydrogenated) carbon films deposited at room temperature in the region of 1000–1700 cm⁻¹ is discussed in this paper. Possible interpretations of the linewidths, positions of the ‘‘G’’ graphite peak and ‘‘D’’ disordered peak, and their intensity ratios are examined using results obtained from magnetron sputtered and magnetic field enhanced plasma deposited films. It is shown that even small ‘‘clusters’’ of condensed benzene rings (cluster size below 20 Å) in carbon films can explain the observed Raman scattering. Besides the care that should be taken in the correct interpretation of Raman results, the utility of Raman scattering in obtaining an estimate of cluster sizes in amorphous (hydrogenated) carbon films is discussed. Carbon films prepared by magnetron sputtering show two additional Raman features at 1180 and 1490 cm⁻¹ in addition to the G and D peaks. It is shown that a correlation exists between the 1180 cm⁻¹ peak and the sp³ content in the films. © 1996 American Institute of Physics.