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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Lokální optické a elektrické charakteristiky optoelektronických součástek / Local optical and electrical characteristics of optoelectronic devices

Škarvada, Pavel January 2012 (has links)
Solar energy conversion, miniaturization of semiconductor devices and associated lifetime, reliability and efficiency of devices are the basic premise of this work. This work is focused on the study of optoelectronic devices especially solar cells and its nondestructive diagnostic. Solar cells are advantageous for study mainly because the pn junction is located near the surface and contains a lot of inhomogeneities. It has been difficult until recently to investigate their local physical (electrical and optical) parameters due to the size of inhomogeneities. Behavior of inhomogeneities can be well understood with knowledge of its local properties. Establishment of measurement workplace, that satisfies requirements for measurement of local emission and optically induced current measurement, allows us detection and localization of inhomogeneities with spatial resolution more or less 100 nm. The core of thesis is characterization of imperfection using nondestructive techniques in the macroscopic region but primarily in microscopic region using scanning probe microscopy. Integral parts of the work are characterization techniques for photoelectrical devices, microscopic techniques and data processing. Scanning near-field optical microscope is used for the purpose of microscopic characterization such as topography, local optical, photoelectrical and electrooptical properties of structures in high spatial resolution. Locally induced current technique, current voltage characteristics, emission from reversed bias pn junction measurement including its thermal dependence are used for samples investigation in macroscopical region. It is possible to localize defects and structure inhomogeneity using mentioned techniques. Localised defects are consequently analyzed for composition and measured using electron microscopy. Specific outputs of work are classification of photoelectric devices defects and specification of nondestructive characterization techniques used for defect detection. Experimental characterization techniques are described together with defects measurement procedures. The key output is the catalog of serious defects which was detected. Particular defects of samples are shown including describe of its properties and physical meaning.
22

Studium chování vybraných hornin při působení vysokých teplot / Study of the behavior of selected rocks at high temperatures

Holanec, Aleš January 2022 (has links)
The diploma thesis deals with the observation and diagnostics of transformations that take place in stone slabs of different mineralogical composition during heating to high temperatures. The theoretical part of the thesis deals with a summary of available information about selected types of rocks. Furthermore, it presents findings from the experimental thermal loading of a granite sample. The principles and instruments of laboratory experimental methods that are used to judge the resistance of rocks are described in detail. In the experimental part, the testing methodology is proposed, the procedure of production of rock test specimens is described and the way in which the thermal loading of stone slabs took place is explained. The results of the experiments are shown in the tables and graphs. A comparison of individual tests and properties of selected samples and evaluation of the obtained results is performed.
23

Etude ultra-sensible en phase de nano-structures par interferométrie optique à balayage en champ proche / A study on ultra-sensitive phase in nano-structures by near-field scanning optical interferometry

Mok, Jinmyoung 26 March 2015 (has links)
La construction d’un NSOM, dans ce manuscrit de thèse, est décrite en détail. Lacombinaison du système NSOM construit avec un interféromètre est proposée afin d’accéderà des mesures de phase, à la fois de ultra-haute sensibilité mais également de très granderésolution spatiale. Le nom de l’instrument développé est un interferomètre optique àbalayage en champ proche (NSOI, pour l’acronyme en anglais). Le principe est basé surl’utilisation d’un diapason accordable en cristal de quartz, sur lequel se trouve une pointe,afin de sonder le matériau étudié. La mesure de la force de cisaillement de la pointe sondeau voisinage de la surface permet d’assurer la régulation et la stabilité de la distance depositionnement de la pointe par rapport à la surface considérée. Le dispositif est construit encombinant différents éléments électroniques pilotés par un logiciel développé en langageLab-VIEW. Le bruit de la mesure en NSOI est supprimé par un calcul simple basé sur lathéorie de l’optique ondulatoire et des interférences associées. Le système permet deréaliser des mesures optiques en champ proche ainsi que la détermination en hauterésolution de la phase du champ optique. L’échantillon SNG01 (l’un des réseaux utilisés pourcaractériser notre microscope à balayage en champ proche), ainsi que des disques optiques(CD, DVD and disques blu-ray) ont été utilisés pour tester la faisabilité et les performancesde notre système.Dans ce manuscrit de thèse, le graphène et les monocouches de MoS2 sont étudiés. Nous montrons qu’une épaisseur à l’échelle atomique peut être résolue par notresystème NSOI, avec l’utilisation de l’algorithme de suppression du bruit de mesure. Lesjoints de grain du graphène sont observés à grande échelle, via la technique d’imagerie parcollection en champ proche et par la réalisation de cartographies de phase. En particulier,les tensions internes à une couche de graphène sont observées, uniquement dans le casd’une imagerie de phase. / In this thesis, near-field scanning optical interferometry (NSOI), which combinesNSOM with interferometer, is proposed for the phase measurement. The shear-forcedetection scheme is applied for distance regulation. The hardware of the systemis constructed by combining various electronic devices, and the operating softwareis coded by LabVIEW. Unwanted background signal is removed by simple calculationbased on interference theory. By using this, the near-field optical measurementand the ultra-sensitive phase investigation of nano-materials are performed. 2D materialssuch as graphene and monolayer MoS2 are investigated. It is shown thatatomic-scale thickness can be resolved by the NSOI. Especially, the grain boundariesof graphene and the seed of MoS2 can be found by phase detection. In addition,direct laser writing (DLW) on silver-containing glass is observed by using NSOM,and NSOI. For the first time, the writing threshold is correlatively observed in thefluorescence imaging and the near-field phase image.

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