J. Wróbel

ZnTe nanowires grown on GaAs(100) substrates by molecular beam epitaxy

ZnTe nanowires with an average diameter of about 30nm and lengths above 1μm were grown on GaAs(100) substrate by molecular beam epitaxy. The growth process was based on the Au-catalyzed vapor-liquid-solid mechanism. A thin gold layer (3–20A thick) annealed in high vacuum prior to the nanowire growth was used as a source of catalytic nanoparticles. The nanowires are inclined about 55° to the (100) substrate surface normal. They have a zinc-blende crystal structure and their growth axis is ⟨111⟩.

Cathodoluminescence study of diluted magnetic semiconductor quantum well/micromagnet hybrid structures

Cathodoluminescence (CL) was studied in hybrid structures consisting of a diluted magnetic semiconductor (DMS) Cd1−xMnxTe (x=0.06 and 0.09) quantum well buried 300 A below the surface on which Fe islands with micrometric dimensions were deposited. The CL at T=10 K collected from areas far away from the Fe island was consistent with the photoluminescence spectra obtained prior to Fe deposition as were the raster scans and spot excited CL spectra taken in nonmagnetized structures close to the Fe islands. After a magnetization at a magnetic field of 3 T, the CL peak related to DMS quantum well (QW) shifts by up to 4 meV to lower energy only when the exciting beam is focused close to edges of an island. The observed shifts are interpreted as due to a fringe field, affecting the DMS QW, of magnetic domains formed in the Fe islands. The experiments prove a feasibility of the concept of usage of the fringe fields to achieve further confinement of excitons in submicron DMS/ferromagnet hybrid structures.

Ordered magnetic phase in Cd1-xMnxTe/Cd1-y-zMgyZnzTe : N heterostructures: magnetooptical studies

Photoluminescence magnetospectroscopy is employed to examine the low-temperature magnetic phase that is induced by the carrier-mediated ferromagnetic exchange interaction in modulation-doped Cd1-xMnxTe quantum well. Unusual properties of the domain structure are linked to tendency towards spin-density wave formation in this low-dimensional magnetic system

MAGNETOCONDUCTANCE NOISE AND IRREVERSIBILITIES IN SUBMICRON WIRES OF SPIN-GLASS N+-CD1-XMNXTE

Signatures of spin-glass freezing such as the appearance of 1/f conductance noise, the recovery of universal conductance fluctuations, aging, as well as magnetic and thermal irreversibilities are detected in mesoscopic wires of CdMnTe:I at millikelvin temperatures. Spectral characteristics of conductance time series are consistent with the droplet model of short-range spin-glasses.

Spin Filtering in a Hybrid Ferromagnetic-Semiconductor Microstructure

We fabricated a hybrid structure in which cobalt and permalloy micromagnets produce a local in-plane spin-dependent potential barrier for high-mobility electrons at the GaAs/AlGaAs interface. Spin effects are observed in ballistic transport in the range of tens of mT of the external field and are attributed to switching between Zeeman and Stern-Gerlach modes--the former dominating at low electron densities.

Resonant spectroscopy of II-VI self-assembled quantum dots: Excited states and exciton-longitudinal optical phonon coupling

Using resonantly excited photoluminescence (PL) along with photoluminescence excitation (PLE) spectroscopies, we study the carrier excitation processes in

Exciton spectroscopy of single CdTe and CdMnTe quantum dots

\mathrm{CdTe}∕\mathrm{ZnTe}

Intermediate phase at the metal-insulator boundary in a magnetically doped two-dimensional electron system

and

Disorder suppression and precise conductance quantization in constrictions of PbTe quantum wells

\mathrm{CdSe}∕\mathrm{ZnSe}

2D and 1D electron transport in hybrid ferromagnet–semiconductor microstructures

self-assembled quantum dots (QDs). PLE spectra of single