Capacitance spectroscopy of InAs self-assembled quantum dots

Capacitance spectroscopy is used to study electronic properties of self-assembled InAs quantum dots. The capacitance-voltage, C(V), measurements in combination with the magneto-capacitance, C(B), results make it possible to investigate the electrostatic profile of a series of single-barrier n-i-n GaAs/AlAs/GaAs heterostructures incorporating a layer of self-assembled InAs quantum dots in the AlAs barrier. We find that the negative charge associated with electron filling of the dots is closely compensated by a positive charge in the AlAs barrier, which we ascribe to ionised defects or impurities, possibly in association with the quantum dots. It is shown the compensation degree considerably depends on the growth conditions.Ємнiсна спектроскопiя використується для дослiдження електронних властивостей само-органiзованих InAs квантових точок. Вимiрювання вольт-фарадних характеристик, C(V), одночасно з даними по магнето-емностi, C(B), дозволяють дослiджувати електростатичний профiль однобар.єрних p-i-n GaAs/AlAs/GaAs гетероструктур, якi мiстять в AlAs бар.єрі шар само-органiзованих InAs квантових точок. Ми визначили, що негативний заряд, пов.язаний з заповненням квантових точок електронами, майже повнiстю компенсується позитивним зарядом в AlAs бар.єрi, що, на нашу думку, пов.язано з iонiзованими дефектами чи домiшками, якi обумовлені квантовими точками. Показано, що мiра компенсацiї суттєво залежить вiд ростових умов.Емкостная спектроскопия используется для исследования электронных свойств само-организованных InAs квантовых точек. Измерение вольт-фарадных характеристик, C(V), совместно с данными по магнето-емкости, C(B), позволяют исследовать электростатический профиль однобарьерных p-i-n GaAs/AlAs/GaAs гетероструктур, содержащих в AlAs барьере слой само-организованных InAs квантовых точек. Мы установили, что отрицательный заряд, связанный с заполнением квантовых точек электронами, почти полностью компенсируется положительным зарядом в AlAs барьере, который, по нашему мнению, связан с ионизованными дефектами или примесями, обусловленными квантовыми точками. Показано, что степень компенсации существенно зависит от ростовых условий

History of clinical transplantation

How transplantation came to be a clinical discipline can be pieced together by perusing two volumes of reminiscences collected by Paul I. Terasaki in 1991-1992 from many of the persons who were directly involved. One volume was devoted to the discovery of the major histocompatibility complex (MHC), with particular reference to the human leukocyte antigens (HLAs) that are widely used today for tissue matching.1 The other focused on milestones in the development of clinical transplantation.2 All the contributions described in both volumes can be traced back in one way or other to the demonstration in the mid-1940s by Peter Brian Medawar that the rejection of allografts is an immunological phenomenon.3,4 © 2008 Springer New York

Information and digital literacies; a review of concepts

A detailed literature reviewing, analysing the multiple and confusing concepts around the ideas of information literacy and digital literacy at the start of the millennium. The article was well-received, and is my most highly-cited work, with over 1100 citations

Giant magnetoresistance induced by magnetic barriers

We present experimental results for hybrid ferromagnet/semiconductor devices in which 2D electrons propagate through sub-micron width magnet barriers. Magnetoresistances, MR, of similar to ∼1000% are found at low temperatures and similar to ∼1% at room temperature. We compared the measured behavior with numerical calculations and give the conditions needed to achieve large room temperature MR

Many-body blockade of resonant tunneling of two-dimensional electrons

Contains fulltext : 27704.pdf (publisher's version ) (Open Access

Dissociation of indirect excitons: Discontinuity and bistability in the tunnel current of single-barrier heterostructures

Contains fulltext : 115669.pdf (publisher's version ) (Open Access

Observation of the fractional quantum Hall effect in GaAs-(Ga, Al)As quantum well structures

Contains fulltext : 112793.pdf (publisher's version ) (Open Access

DIRECT OBSERVATION OF ORBITAL DISSIPATION AND SUPERFLOW COLLAPSE IN 3He-A

Des expériences de pendule de torsion dans lesquelles le temps de relaxation orbitale est comparable à la période d 'oscillation montrent une atténuation fortement dépendante de l'amplitude dans 3He-A qui est absente dans 3He-B A forte amplitude, la densité superfluide apparente tend vers zéro, suggérant l'effondrement du courant superfluide comme l 'ont décrit Bhattacharyya, Ho et Mermin.Torsion pendulum experiments in which the orbital relaxation time is comparable with the oscillation period show strong amplitude dependent damping in 3He-A that is absent in 3He-B. At large amplitudes the apparent superfluid density decreases towards zero, suggesting collapse of superflow as described by Bhattacharyya, Ho and Mermin