L. Nosenzo

Infra-red properties of bulk heavily doped silicon

SummaryIn this work reflectance (R) and thermoreflectance (TR) spectra in the infra-red of bulk P and B heavily doped silicon samples are reported and discussed. The values of the scattering time and of the effective mass, as well as the temperature derivative of the plasma frequency, scattering time and high-frequency dielectric constant are extracted from the data and analysed in terms of free-carrier-photon and free-carrier-impurity interaction.RiassuntoIn questo lavoro sono riportati e discussi gli spettri di riflettanza (R) e termoriflettanza (TR) in infrarosso di campioni di silicio drogati pesantemente per diffusione con P e B. Dai dati sono ricavati i valori dei tempi di rilassamento e della massa effettiva, come pure la derivata in temperatura della frequenza di plasma, del tempo di rilassamento e della costante dielettrica ad alta frequenza, che sono analizzati sulla base delle interazioni fra portatori liberi e fononi e fra portatori liberi e impurezze.

Reflectivity and electronic structure of Pd silicides

The reflectivities of Pd and Pd silicides have been measured from 0.5 to 6 eV and compared with the existing density of states and band calculations as well as with the optical spectra of other silicides. The rather complex spectra resulting from the superposition of the free carrier response and inter-band transitions are discussed and some indications concerning their interpretation are drawn.

Fundamental optical properties of In halides

Abstract Reflectance and thermoreflectance spectra between 2 and 9 eV have been measured for InBr and InI crystals. A correlation between optical structures and electronic levels is proposed taking into account of the X-ray photoelectron spectroscopy data and of the expected similarity of In and Tl halides band scheme.

Optical absorption of Co(II) ion in CoxZn1-xIn2S4 (0.07 ⩽ x ⩽ 0.46) solid solution

Abstract The d-d spectra of Co x Zn 1- x In 2 S 4 solid solution at 300 and 77 K have been interpreted on the assumption that a tetrahedrally coordinated Co 2+ ion predominates. The analysis of the absorption edge region allowed to make some comments on the cationic disorder within this solid solution.

Influence of the magnetic transition on the optical properties of CrBr3

Abstract Reflectance and thermoreflectance spectra of the magnetic insulator CrBr3 have been measured in the para- and ferromagnetic phases. Below the Curie temperature the structure at ≅ 7.30 eV splits into two components separated by ≅ 0.27 eV. This doublet is ascribed to an optical excitation involving the exchange split conduction band.

Thermoreflectance investigation of heavily doped silicon

Abstract The effect of the presence of high concentrations of dopants on the interband spectra of silicon has been studied by means of thermoreflectance. Heavy doping has been performed through ion implantation and eventually laser annealing. From the analysis of the thermoreflectance spectra a wide set of parameters characterizing in particular the E1andE2 structures has been obtained.

Far-infrared optical properties of CrCl3 and CrBr3

Abstract We measured the far-infrared transmittance and reflectance spectra of the layered compounds CrBr3 and CrCl3 at normal and oblique incidences and at room temperature. The results are compared with the spectra from previous Raman measurements and are analyzed on the basis of the unit cell group method applied to the diperiodic crystalline structure of a single layer. A fit of the CrBr3 reflectivity spectrum with damped Lorentzian oscillators is made which also allows us to evaluate the static dielectric constant ϵ0.

Optical Properties of Heavily Doped Semiconductor Layers

It is shown that a coupled study of the structures due to interband transitions and of the free carrier response in heavily doped semiconductors gives a combined picture of crystal order, free carrier concentration, effective mass and relaxation time. As, P and B ion implanted and laser annealed Si crystals are investigated. Reflectance measurements on samples with free carrier concentrations in the range 1019-1021 cm-3 are reported and discussed.

Thermoreflectance lineshape modifications induced by the magnetic ordering

Abstract Recently strong modifications in the intensity and the shape of thermoreflectance (TR) spectra in ferromagnetic crystals near the transition temperature have been reported. In this letter we propose a phenomenological model, based on the band splitting by the molecular field, which rather well explains the changes observed in the TR spectrum of CrBr3 near 7eV.

Optical Spectroscopy in Transition-Metal Dichalcogenides

The optical spectroscopy of layered and in particular of transition metal dichalcogenides is an interesting and stimulating subject which has played a major role in the recent developments of solid state physics. A detailed investigation of the optical structures due to interband transitions has been carried out by means of reflectance and thermoreflectance. Pure compounds and mixed systems have been studied in some detail. Among the latter ones, a particular attention has been devoted to Ti 1-x Hf x Se 2, which changes from semimetallic to semiconducting as a function of composition and shows an anomalous evolution of the energy position of its main spectral features versus lattice and other structural parameters. The effect of phase transitions like charge density waves on the optical response, and in particular on the plasma resonance, free carrier absorption, energy gap etc., is also studied and discussed.