Stefan R. Lüthi Department of Chemistry and Biochemistry, The University of Bern, Freiestrasse 3, 3012 Bern, Switzerland (Received 2 December 1998) We report the first observation of intrinsic optical bistability in CsCdBr3:1% Yb31 and show, using site-selective spectroscopy, that only the asymmetric, strongly coupled Yb31 ion-pair minority site gives rise to hysteresis of near-infrared and coo...

The two-photon absorption (TPA) cross sections (δ) for tungsten(0) arylisocyanides (W(CNAr)6) were determined in the 800-1000 nm region using two-photon luminescence (TPL) spectroscopy. The complexes have high TPA cross sections, in the range 1000-2000 GM at 811.8 nm. In comparison, the cross section at 811.8 nm for tris-(2,2'-bipyridine)ruthenium(ii), [Ru(bpy)3]2+, is 7 GM. All measurements we...

Graphene quantum dots (GQDs) have attracted considerable interest due to their unique physicochemical properties and various applications. For the first time it is shown that GQDs surface-functionalized with hydrocarbon chains (i.e., amphiphilic GQDs) self-assemble into unilamellar spherical vesicles in aqueous solution. The amphiphilic GQD vesicles exhibit multicolor luminescence that can be r...

A novel structure containing self-assembled, unstrained GaAs quantum dots is obtained by combining solid-source molecular beam epitaxy and atomic-layer precise in situ etching. Photo-luminescence (PL) spectroscopy reveals light emission with very narrow inhomogeneous broadening and clearly resolved excited states at high excitation intensity. The dot morphology is determined by scanning probe m...

Pseudomorphic Ga12xInxN/GaN single heterostructures in the composition range 0,x,0.2 have been investigated by photoreflectance and photoluminescence spectroscopy. Strong Franz–Keldysh oscillations near the band gap of the ternary film are observed and attributed to a large constant piezoelectric field of up to 0.63 MV/cm. This allows an accurate determination of the electric field. A significa...

We used a combination of scanning electron microscopy, laser scanning confocal microscopy and luminescence spectroscopy to correlate the emission properties of anodized porous silicon (PS) with film morphology in samples that have undergone solvent evaporation-induced collapse of the underlying porous structure. Several PS samples were investigated as a function of the current density (J) and t...