Search results for "wells"

Current status of AlInN layers lattice-matched to GaN for photonics and electronics

2007

We report on the current properties of Al1-x InxN (x approximate to 0.18) layers lattice- matched ( LM) to GaN and their specific use to realize nearly strain- free structures for photonic and electronic applications. Following a literature survey of the general properties of AlInN layers, structural and optical properties of thin state- of- the- art AlInN layers LM to GaN are described showing that despite improved structural properties these layers are still characterized by a typical background donor concentration of ( 1 - 5) x 10(18) cm(-3) and a large Stokes shift (similar to 800 meV) between luminescence and absorption edge. The use of these AlInN layers LM to GaN is then exemplified …

Blue lasing at room temperature in high quality factor GaN/AlInN microdisks with InGaN quantum wells

2007

The authors report on the achievement of optically pumped III-V nitride blue microdisk lasers operating at room temperature. Controlled wet chemical etching of an AlInN interlayer lattice matched to GaN allows forming inverted cone pedestals. Whispering gallery modes are observed in the photoluminescence spectra of InGaN/GaN quantum wells embedded in the GaN microdisks. Typical quality factors of several thousands are found (Q>4000). Laser action at similar to 420 nm is achieved under pulsed excitation at room temperature for a peak power density of 400 kW/cm(2). The lasing emission linewidth is down to 0.033 nm.

Temperature dependence of the effective mobility edge and recombination dynamics of free and localized excitons in InGaP/GaAs quantum wells

2003

3 páginas, 1 figura.-- Comunicación presentada al Proceedings of the International Conference on Superlattices, Nano-structures and Nano-devices ICSNN 2002 o-structures and Nano-devices ICSNN 2002.

Reazione catalitica e fotocatalitica di disidratazione in fase gas-solido del 2-propanolo in presenza di eteropoliacidi "Keggin" e "Wells-Dawson" sup…

2015

La disidratazione catalitica e fotocatalitica di 2-propanol a propilene è stata effettuata usando eteropoliacidi di Keggin H3PW12O40 (PW12) e Wells-Dawson H6P2W18O60 (P2W18). Sono stati utilizzati sia supportani che non. Materiali binari sono stati preparati per l'impregnazione degli eteropoliacidi su supporti commerciali: SiO2 (Aldrich) e TiO2 (Evonik P25). I materiali sono stati caratterizzati e la loro (foto) attività catalitica rispetto alla disidratazione 2-propanol evaluata in regime gas-solido utilizzando un reattore continuo a pressione atmosferica e un range di temperatura fra 60 e 120 ° C. Inoltre, per gli esperimenti fotoassititi il reattore è stato illuminato da un LED UV. Impor…

Study of the photocatalytic activity of Keggin and Wells Dawson heteropolyacids: role of the acidity and of the pseudo-liquid phase regime

2017

Study of the photocatalytic activity of Keggin and Wells Dawson heteropolyacids: role of the acidity and of the pseudo-liquid phase regime

La scoperta del futuro

2021

La scoperta del futuro è un manifesto di futurologia, una spinta giovane, moderna e tecnologica, figlia della scienza del suo tempo, verso una definizione metodica e analitica di un campo di studi tanto incerto quanto affascinante: il futuro. È manifesto anche del lato scientifico di Wells, o meglio della sua volontà di emanciparsi dalla semplice definizione di scrittore di fantascienza per accedere alla fama di scienziato, ambitissima da gran parte degli scrittori della sua epoca, da Jules Verne a Emilio Salgari, da Edgar Allan Poe a Thomas H. Huxley e Arthur Conan Doyle. Per Wells non si tratta di riabilitare la figura degli indovini, tutt’altro, ma di impiantare un campo di analisi ben d…

MR3063436 Reviewed Znojil, Miloslav; Wu, Junde A generalized family of discrete PT-symmetric square wells. Internat. J. Theoret. Phys. 52 (2013), no.…

2014

Brownian motion in trapping enclosures: Steep potential wells, bistable wells and false bistability of induced Feynman-Kac (well) potentials

2019

We investigate signatures of convergence for a sequence of diffusion processes on a line, in conservative force fields stemming from superharmonic potentials $U(x)\sim x^m$, $m=2n \geq 2$. This is paralleled by a transformation of each $m$-th diffusion generator $L = D\Delta + b(x)\nabla $, and likewise the related Fokker-Planck operator $L^*= D\Delta - \nabla [b(x)\, \cdot]$, into the affiliated Schr\"{o}dinger one $\hat{H}= - D\Delta + {\cal{V}}(x)$. Upon a proper adjustment of operator domains, the dynamics is set by semigroups $\exp(tL)$, $\exp(tL_*)$ and $\exp(-t\hat{H})$, with $t \geq 0$. The Feynman-Kac integral kernel of $\exp(-t\hat{H})$ is the major building block of the relaxatio…

The Time Machine : a material package for using fiction in foreign language teaching

2015

Oppimateriaaleja kaunokirjallisuuden käyttöön lukion vieraan kielen opetuksessa on ollut tarjolla niukasti. Kaunokirjallisuuden lukeminen vieraalla kielellä tarjoaa kuitenkin mahdollisuuden oppia kieltä hauskalla ja mielekkäällä tavalla formaalin opetuksen ulkopuolella, joten sitä opetukseen soveltavalle materiaalille on selvästi tarvetta. Materiaalia, jossa harjoitetaan monipuolisesti jokaista neljää kielitaidon osa-aluetta (lukeminen, kirjoittaminen, puhuminen, kuunteleminen) on myös suhteellisen vähän saatavilla. Kaunokirjallisuuden käytöllä vieraan kielen opetuksessa on useita etuja. Se tarjoaa helposti käytettävissä olevaa autenttista opetusmateriaalia, herättää oppilaiden kiinnostusta…

Crystalline-Size Dependence of Dual Emission Peak on Hybrid Organic Lead-Iodide Perovskite Films at Low Temperatures

2018

In this work, we have investigated the crystalline-size dependence of optical absorption and photoluminescence emission of CH3NH3PbI3 films, which is necessary to identify the potential practical applications of the gadgets based on perovskite films. This study was carried out at low temperatures to minimize the extra complexity induced by thermal effects. The purpose was to clarify the origin of the dual emission peak previously reported in the literature. We found that the grain size is responsible for the appearance or disappearance of this dual emission on CH3NH3PbI3 at low temperatures, whereas we have inferred that the thickness of the perovskite layer is a much more important factor …