PbS in polymers. From molecules to bulk solids

The transition of PbS from molecular to bulk form has been observed in polymer films. As the particle size decreases the band gap shifts to the blue and eventually approaches the transition energy of the first allowed excited state, X→A, of a PbS molecule. Discrete absorption bands also appear. The electron‐hole‐in‐a‐box model with effective mass approximation cannot explain the observed size dependence. We have developed two theoretical models, both including the effect of band nonparabolicity, that successfully explain the observed size dependence down to about 25 A.

[1]  L. Esaki,et al.  The Growth of a GaAs–GaAlAs Superlattice , 1973 .

[2]  S. C. O'brien,et al.  C60: Buckminsterfullerene , 1985, Nature.

[3]  A. J. P. Taylor,et al.  X-ray metallography , 1961 .

[4]  D. Hwang,et al.  Clusters in solution: Growth and optical properties of layered semiconductors with hexagonal and honeycombed structures , 1986 .

[5]  R. Knox,et al.  Theory of excitons , 1963 .

[6]  A. Henglein,et al.  Photochemistry of colloidal semiconductors. Onset of light absorption as a function of size of extremely small CdS particles , 1986 .

[7]  J. Fendler,et al.  In situ generated colloidal semiconductor CdS particles in dihexadecyl phosphate vesicles: quantum size and asymmetry effects , 1986 .

[8]  Marvin L. Cohen,et al.  ELECTRONIC BAND STRUCTURE AND OPTICAL PROPERTIES OF PbTe, PbSe, AND PbS , 1973 .

[9]  Jeremy J. Ramsden,et al.  Luminescence of colloidal cadmium sulfide particles in acetonitrile and acetonitrile/water mixtures , 1985 .

[10]  E. K. Parks,et al.  Generation of continuous beams of refractory metal clusters , 1982 .

[11]  D. Whitten,et al.  Photophysics of quantized colloidal semiconductors. Dramatic luminescence enhancement by binding of simple amines , 1986 .

[12]  L. Brus,et al.  Hybrid electronic properties between the molecular and solid state limits: Lead sulfide and silver halide crystallites , 1985 .

[13]  G. Herzberg Molecular Spectra and Molecular Structure IV. Constants of Diatomic Molecules , 1939 .

[14]  Tijana Rajh,et al.  Size quantization in small semiconductor particles , 1985 .

[15]  Robert Zannetti,et al.  Landolt-bornstein, new series , 1974 .

[16]  A. Kaldor,et al.  Photoionization measurements on isolated iron-atom clusters , 1983 .

[17]  Norman Herron,et al.  Optical properties of CdS and PbS clusters encapsulated in zeolites , 1987 .

[18]  Andrew Streitwieser,et al.  Molecular orbital theory for organic chemists , 1961 .

[19]  E. Nixon,et al.  Vibronic spectra of matrix-isolated lead sulfide , 1975 .

[20]  C. R. Berry Structure and Optical Absorption of AgI Microcrystals , 1967 .

[21]  J. Burdett From bonds to bands and molecules to solids , 1984 .

[22]  A. I. Ekimov,et al.  Quantum size effect in semiconductor microcrystals , 1985 .

[23]  Y. Wang,et al.  Degenerate four-wave mixing of CdS/polymer composite , 1987 .