C. H. Perry

Strong room‐temperature infrared emission from Er‐implanted porous Si

This communication demonstrates a strong, room‐temperature (RT), infrared (IR) (1.54 μm) emission from Er‐implanted red‐emitting (peaked at 1.9 eV) porous silicon (Er:PSi). Erbium was implanted into porous Si, bulk Si, and quartz with a dose of 1015/cm2 at 190 keV and annealed for 30 minutes in N2 at temperatures ranging from 500 °C to 900 °C under identical conditions. No RT IR emission was observed from Er implanted quartz and silicon after annealing at 650 °C (although after annealing at 900 °C very weak emission was observed from quartz at 9 K). The highest RT emission intensity at 1.54 μm was from Er:PSi with a peak concentration of 1.5×1020/cm3 and annealed at 650 °C. Even the luminescence intensity from Er:PSi annealed at 500 °C was 26 times higher than that observed from Er‐implanted quartz at 400 keV and annealed at 900 °C. A reduction in photoluminescence (PL) intensity of about a factor of two from Er:PSi over the 9 to 300 K temperature range was observed which is consistent with Er in wide ban...

Infrared spectra in nonstoichiometric yttria‐stabilized zirconia mixed crystals at elevated temperatures

Infrared (IR) reflectivity measurements were undertaken on pure ZrO2 and stabilized ZrO2⋅Y2O3 solid solutions containing 3‐, 4‐, 7‐, 12‐, and 20‐wt.% Y2O3 over 10–900 cm−1 region as a function of temperature up to 1400 °C. The observed IR active phonons are related to the phase transitions that depend on composition and temperature. Good agreement was achieved among IR, Raman scattering, and neutron scattering investigations. An IR reflectivity enhancement from 42% to 60% in the low‐frequency region (10–110 cm−1) was found as the monoclinic(M)‐tetragonal(T) martensitic transition was completed in pure ZrO2 and ZrO2⋅3‐wt.% Y2O3.

Photoluminescence spectra from porous silicon (111) microstructures: Temperature and magnetic‐field effects

Visible and near‐infrared (IR) photoluminescence emission spectra (0.9–3.0 eV) from p‐type porous Si(111) microstructures are reported as a function of temperature and magnetic field. The visible peak located at 1.84 eV at 4 K shifted to ∼1.56 eV at 575 K where it disappeared; the intensity reached a maximum value at ∼150 K. The photoluminescence spectrum showed no measurable shift in the peak position with magnetic field from 0 to 15 T. Strong IR intrinsic band‐to‐band emission above and below the bulk silicon band gap at ∼1.09 eV at 300 K was observed. This luminescence was found to be enhanced by two orders of magnitude or more over the IR spectrum from an unanodized wafer.

Room-temperature electro-optic up-conversion via internal photoemission

We describe the fabrication and operation of a device which performs linear optical up-conversion at room temperature. The mechanism for up-conversion is based on internal photoemission from a Schottky contact. We then describe the voltage dependence of this device and interpret it in terms of total energy conservation. Although an AlGaAs/GaAs system is employed here, the functionality is not material-specific and therefore should be widely applicable to different materials systems, such as GaN/InGaN.

The Raman spectrum of ferroelectric SbSI

Abstract The polarized Raman spectrum of SbSI has been studied in both the paraelectric and ferroelectric phases. The frequencies and symmetries of most of the Raman active phonons in the paraelectric phase have been determined. A strongly temperature dependent A mode has been observed in the ferroelectric phase which completely accounts for the temperature dependence of the dielectric constant along the ferroelectric axis.

Spectroscopy of Landau transitions of two-dimensional electron gases

Abstract We have employed resonant inelastic light scattering spectroscopy to study electronic transitions in multilayer two-dimensional electron gases in magnetic fields of 4–14 T. From polarized spectra, we have evidence for both single particle Landau transitions (Δl = 1 and Δl = 2) as well as their collective counterparts. We show the variation of intensities with B and the resonant behavior, but are unable to identify a scattering mechanism.

Investigation of near interface properties in semi‐insulating InP substrates with epitaxial grown InGaAs and InAlAs by photoreflectance

An extensive photoreflectance (PR) study has been done on a series of undoped and n‐type, InGaAs and InAlAs molecular beam epitaxy (MBE) grown layers with different In mole fractions, and epilayer thicknesses on Fe‐doped semi‐insulating (SI)‐InP substrates. Three substrate features were observed in the spectra. From investigations of the temperature dependence, time constant dependence, and an additional cw light beam intensity dependence, they were identified as an excitonic transition from the substrate, a free electron transition near the interface which gives a Franz–Keldysh oscillation, and a transition from the spin–orbit split‐off valence band. The Franz–Keldysh effect indicates that a temperature dependent built‐in electric field is formed near the interface. The dependence of the field on doping concentration, strain, or epilayer composition (band gap) was insignificant. The PR signal from a SI‐InP wafer after a pre‐MBE‐growth heating was found to be strongly enhanced over that from an untreated ...

Quasi-elastic scattering due to fast oxygen diffuson in yttria stabilized zirconia

Abstract Evidence for fast oxygen diffusion at high temperatures in single crystal ZrO 2 containing 12 mol % Y 2 O 3 is presented from quasi-elastic light scattering data. Lattice vacancies are responsible for the enhanced ionic diffusion and the structural disorder. In the temperature range investigated we estimate the barrier activation energy for the jumping of oxygen vacancies to be 0.25 eV. At 1500°K the jump time is ∼ 4 × 10 −12 sec., the diffusion constant is ∼ 3.26 × 10 −5 cm 2 /sec. and the conductivity is ∼ 0.24 (Ωcm) −1 .

Photoreflectance studies of GaAs containing a Si‐δ‐doping layer

The electronic structure of several n‐type GaAs samples containing ‘‘δ‐doping’’ layers of Si have been studied using photoreflectance (PR) spectroscopy. Well‐defined oscillatory features due to electronic transitions well above the band gap are observed at 300 K and identified as Franz–Keldysh oscillations. The energy spacing and the intensity of the oscillations decrease with decreasing temperature as a consequence, we believe, of changes in the electric field due to the surface charges. Self‐consistent energy‐band calculations support the interpretation that the oscillatory structure is due to Franz–Keldysh effects. The imposition of magnetic fields up to 15 even at room temperature has a pronounced influence on the PR spectrum. Parallel fields suppress the oscillatory structure but cause a large increase in the PR peaks near the GaAs energy gap. At 4.2 K Landau‐like spectral features are observed for fields applied perpendicular to the doping layer.

Infrared and Raman spectra of lunar samples from Apollo 11, 12 and 14

We report the room temperature infrared reflectance spectra of several lunar surface rocks in the form of polished slices or butt ends. The spectra were obtained over the frequency range 20-2000 cm−1 throughout the mid and far infrared (5-500µ) region of the electromagnetic spectrum where the fundamental internal and lattice vibrational modes of all minerals and rocks occur.Some fines samples were examined as pressed pellets and their reflectivities compared with the bulk samples. Several terrestrial minerals and rocks were also investigated. Kramers-Kronig analyses of these reflectance spectra were undertaken and the dispersion of the dielectric response (ε′ and ε″) and the optical constants (n andk) have been determined over this frequency range. The low frequency and high frequency (infrared) dielectric constants were also calculated from the reflectance data.Raman light scattering measurements were made on all the samples supplied from the first three Apollo missions. Large background scattering proved to be the greatest experimental problem. Successful spectra in nearly all cases were obtained from small crystalline inclusions imbedded in the main ground mass. Some crystalline bulk rocks containing many very fine inclusions gave identifiable spectra and at least three different types were obtained.