Molecular beam epitaxial growth of III-V semiconductor ... - KOBRA

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Experimental Growth and Characterization Techniques of the specimen which is then magnied by the remaining imaging lenses and projected onto the viewing device. Figure 4.6: Transmission electron microscopy. (a) Electron beam prole passing through dierent lenses and apertures. (b) Real TEM scheme with its main components embedded in vacuum column or chamber [74]. When electrons impinge on the specimen, this can cause some of the electrons are absorbed as a function of the thickness and composition of the specimen; these cause what is called amplitude (or mass thickness) contrast in the image. Other electrons are scattered over small angles, depending on the composition and structure of the specimen; these cause what is called phase contrast in the image. However, in crystalline specimens, the electrons are scattered in very distinct directions that are a function of the crystal structure; these cause what is called diraction contrast in the image. In a standard TEM, mass thickness is the primary contrast mechanism for non-crystalline (biological) specimens, while phase contrast and diraction contrast are the most important factors in image formation for crystalline specimens (most non-biological materials). Therefore, collimated high-energy electrons from a condenser lens impinge on the semiconductor specimen and are transmitted through it. The electrons are scattered into 60
4.4 High Resolution Transmission Electron Microscopy particular directions by the crystalline sample according to the Bragg law for diraction. These diracted beams are brought into focus at the focal plane for the objective lens. In the diraction mode, the rst intermediate lens is focused on the back focal plane of the objective lens, thus capturing the diraction pattern. This diraction pattern is magnied and projected by the combination of the intermediate and projection lenses. The diraction pattern displayed on the screen comprises an array of spots, each corresponding to a particular diraction vector g. The diraction mode is used to index the diraction beams and to facilitate the selection of the diraction spots to be used in ultimately forming an image [73]. In the imaging mode, the intermediate lens is focused on the inverted image of the sample formed by the objective lens. This image is magnied and projected onto the screen with an overall magnication of up to million times. An aperture at the back focal plane of the objective lens is used to select only one diracted beam to form the image. If the beam transmitted directly through the image is chosen, a bright-eld image results. If one of the diracted beams is chosen to form the image, then a dark-eld image is produced [31]. All the TEM results presented in this thesis are performed by our project partner Paul Drude Institute (PDI) in Berlin. This TEM results conducted via the JEOL JEM-3010, which is a 300 kV transmission electron microscope with a LaB6 electron source. It is equipped with an ultra-high resolution (UHR) pole piece that results in a point resolution of 0.17 nm. 61
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Molecular Beam Epitaxial Growth of
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Gutachter (Supervisors): 1. Prof. D
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patterns indicating a 2D smooth sur
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(MEE = migration enhance epitaxy) u
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viii
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CONTENTS 3.4.4 Planar Defects Assoc
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CONTENTS xii
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Introduction thesis a detailed stud
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Introduction 1.1.2 Thesis Approach
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Introduction 1.2 Thesis Outline The
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Theoretical Background of Semicondu
Page 24 and 25: Theoretical Background of Semicondu
Page 36 and 37: Heteroepitaxial Growth of III-V Sem
Page 64 and 65: Experimental Growth and Characteriz
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Page 118 and 119: MBE Growth of InAs and InGaAs Quant
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MBE Growth of InAs and InGaAs Quant
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Optimization of MEE and MBE growth
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Conclusions substrates, respectivel
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REFERENCES [8] J. M. Gerard, O. Cab
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REFERENCES [29] http://www.wmi.badw
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REFERENCES [49] M. R. Brenner: GaP/
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REFERENCES [66] Y. Ishida, T. Takah
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REFERENCES [84] A. Garcia, C. M. Ma
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REFERENCES [100] M. Felici, P. Gall
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REFERENCES [116] H. Usui, H. Yasuda
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REFERENCES [133] Grassman, T. J. Br
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Conferences Contributions: Tariq Al
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Nomenclature
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REFERENCES symbol Descriptions γ f
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like to thank all member of the Ins
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REFERENCES Erklärung Hiermit versi
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Molecular beam epitaxial growth of III-V semiconductor ... - KOBRA

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