Search results for "insulator"
showing 10 items of 228 documents
Critical behavior of Si:P at the metal-insulator transition
1994
A Comment on the Letter by H. Stupp et al., Phys. Rev. Lett. 71, 2634 (1993).
Surface band-gap narrowing in quantized electron accumulation layers.
2010
An energy gap between the valence and the conduction band is the defining property of a semiconductor, and the gap size plays a crucial role in the design of semiconductor devices. We show that the presence of a two-dimensional electron gas near to the surface of a semiconductor can significantly alter the size of its band gap through many-body effects caused by its high electron density, resulting in a surface band gap that is much smaller than that in the bulk. Apart from reconciling a number of disparate previous experimental findings, the results suggest an entirely new route to spatially inhomogeneous band-gap engineering.
Molecular semiconductor-doped insulator (MSDI) heterojunctions: an alternative transducer for gas chemosensing
2009
New organic devices including a heterojunction between a semiconducting molecular material (MS)--lutetium bisphthalocyanine (LuPc2)--and a doped insulator (DI)--copper phthalocyanine (Cu(F(n)Pc), where n = 0, 8, 16)--are designed and studied as transducers for redox-active species sensing.
Subwavelength imaging of field confinement in a waveguide-integrated photonic crystal cavity
2005
A photonic crystal microcavity is designed to obtain an original field distribution inside the cavity and the structure is etched inside a silicon-on-insulator waveguide. Spectral location of the photonic band gap and cavity resonance are identified by using transmittance measurements and by analyzing the light collected by a scanning near-field optical microscope probe exactly positioned on the center of the cavity. The results obtained with the two techniques are in very good agreement. Then the near-field distribution above the device is mapped and light confinement inside the cavity is evidenced. Moreover, this confined light presents some remarkable patterns which clearly correspond to…
Probing magnetism in 2D van der Waals crystalline insulators via electron tunneling
2018
Magnetic insulators are a key resource for next-generation spintronic and topological devices. The family of layered metal halides promises varied magnetic states, including ultrathin insulating multiferroics, spin liquids, and ferromagnets, but device-oriented characterization methods are needed to unlock their potential. Here, we report tunneling through the layered magnetic insulator CrI₃ as a function of temperature and applied magnetic field.We electrically detect the magnetic ground state and interlayer coupling and observe a fieldinducedmetamagnetic transition.The metamagnetic transition results in magnetoresistances of 95, 300, and 550% for bilayer, trilayer, and tetralayer CrI₃ bar…
Topological insulators and thermoelectric materials
2012
Topological insulators (TIs) are a new quantum state of matter which have gapless surface states inside the bulk energy gap. Starting with the discovery of two dimensional TIs, the HgTe-based quantum wells, many new topological materials have been theoretically predicted and experimentally observed. Currently known TI materials can possibly be classified into two families, the HgTe family and the Bi2Se family. The signatures found in the electronic structure of a TI also cause these materials to be excellent thermoelectric materials. On the other hand, excellent thermoelectric materials can be also topologically trivial. Here we present a short introduction to topological insulators and the…
Sequential and site-specific on-surface synthesis on a bulk insulator
2013
cited By 15; International audience; The bottom-up construction of functional devices from molecular building blocks offers great potential in tailoring materials properties and functionality with utmost control. An important step toward exploiting bottom-up construction for real-life applications is the creation of covalently bonded structures that provide sufficient stability as well as superior charge transport properties over reversibly linked self-assembled structures. On-surface synthesis has emerged as a promising strategy for fabricating stable, covalently bound molecular structure on surfaces. So far, a majority of the structures created by this method have been obtained from a rat…
Substrate templating upon self-assembly of hydrogen-bonded molecular networks on an insulating surface.
2012
M olecular self-assembly on insulating surfaces, despite being highly relvant to many applications, generally suffers from the weak molecule–surface interactions present on dielectric surfaces, especially when benchmarked against metallic substrates. Therefore, to fully exploit the potential of molecular self-assembly, increasing the infl uence of the substrate constitutes an essential prerequisite. Upon deposition of terephthalic acid and trimesic acid onto the natural cleavage plane of calcite, extended hydrogen-bonded networks are formed, which wet the substrate. The observed structural complexity matches the variety realized on metal surfaces. A detailed analysis of the molecular struct…
CVD elaboration and in situ characterization of barium silicate thin films.
2010
International audience; This study is concerned with the elaboration of barium silicate thin films by metal organic chemical vapor deposition (MOCVD) and in situ characterization by X-ray photoemission spectroscopy (XPS) with an apparatus connected to the deposition reactor. The difficulty to find an efficient metal organic precursor for barium is described. After characterizations of the selected reactant, Ba(TMHD)2tetraglyme, the development of an original specific vapor delivering source which allows reactant sublimation in the CVD reactor was performed. In the most optimized cases, including use of oxygen introduction during the deposition, barium silicate films were obtained. Moreover,…
On-surface synthesis on a bulk insulator surface
2018
On-surface synthesis has rapidly emerged as a most promising approach to prepare functional molecular structures directly on a support surface. Compared to solution synthesis, performing chemical reactions on a surface offers several exciting new options: due to the absence of a solvent, reactions can be envisioned that are otherwise not feasible due to the insolubility of the reaction product. Perhaps even more important, the confinement to a two-dimensional surface might enable reaction pathways that are not accessible otherwise. Consequently, on-surface synthesis has attracted great attention in the last decade, with an impressive number of classical reactions transferred to a surface as…