Diese Dissertation besteht aus zwei Teilen von Studien. Der erste Teil demonstriert die Steuerung der Elektron-Kern-Spin-Systems in II-VI Halbleiter Quantum Dots (QDs) durch elektrische Ströme über Mikrospulen. Mikrometer-große Leiterschleifen sind auf der Oberseite von Heterostrukturen mit geladenen CdSe/ZnS QDs hergestellt worden. Eine Strominjektion erzeugt magnetische Felder im Bereich von einige 10 mT, welche stark genug sind, um die Hyperfeinwechselwirkung in CdSe QDs modulieren zu können. Der Durchmesser des Spulen im Mikrometer-Bereich ermöglicht die Generation von schnellen Feld transienten im Bereich von wenigen ns. Mit diesen Vorteilen der Mikrospulen werden die Steuerungs des Spins der residenten Elektronen sowie das Auslesen des Kernspinzustandes durch elektrische Impulse nachgewiesen. Der zweite Teil befasst sich mit der Ladungsträger-Spindynamik in ZnO Quantum Well (QW) Strukturen und Epitaxieschichten, die mittels des optischen Übergang von negativ geladenen Exzitonen X− beziehungsweise des am neutralen Donator gebunden Exziton D0X untersucht werden. Der Loch-Spin kann direkt über die zirkular polarisierten Photolumineszenz der beiden Komplexe zurückverfolgt werde. Die Spin-Relaxationszeit von QW und Epiplyer verfolgt werden. Der Spin des Donatorelektronens wird über die Ausbleichung des Spin-selektive Anregungprozesses nachgewiesen. Es werden longitudinale Loch-Spinrelaxationszeiten von 80 bis 140 ps für D0X und X− gefunden. Deutlich längere longitudinalen Elektronen-Spin-Relaxationszeiten in Bereich von mehreren 100 ns werden gefunden, wenn die Hyperfeinwechselwirkung durch ein geeignetes externes Magnetfeld unterdrückt wird. Eine Feldstärke von 2 mT ist groß genug. Dies zeigt den extrem kleinen Wert des Overhauser-Feldes in ZnO auf, der durch die sehr begrenzte Anzahl von magnetischen Kernen in Wechselwirkung mit dem Elektronen innerhalb des Volumens des Donators verursacht wird. / This work is composed of two parts of studies. The first part represents an electron-nuclear spin control in II-VI semiconductor quantum dots (QDs) by electrical currents via micro coils. Micrometer single turn coils are fabricated on top of heterostructures with charged CdSe/ZnSe QDs. Current injection creates magnetic fields in the range of some 10 mT which is strong enough to modulate the hyperfine interaction in CdSe. The micrometer-range diameter of coil allows for generation of fast field transient in the range of few ns. Using these advantages of micro coils, local control of the resident electron spin as well as read out of the nuclear spin state are demonstrated by electrical pulses. The second part presents charged carrier spin dynamics in ZnO quantum wells and epilayers using the optical transition of the negatively charged exciton X− and the neutral donor bound exciton D0X, respectively. The hole spin can be directly traced by the circular polarized photoluminescence of both complexes. The spin relaxation of the resident electrons and donor electrons is accessed via the bleaching of the spin selective excitation process. Longitudinal hole spin relaxation times of 80 and 140 ps are found for D0X and X−, respectively. Much longer longitudinal electron spin relaxation times in the several 100 ns range are uncovered if the hyperfine interaction is suppressed by a proper external magnetic field. A field strength of 2 mT is large enough proving that the extremely small value of the Overhauser field in ZnO caused by the very restricted number of magnetic nuclei interacting with the electron inside the donor volume.

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Blinking dynamics of CdSe/ZnS semiconductor quantum dots (QD) are characterized by (truncated) power law distributions exhibiting a wide dynamic range in probability densities and time scales both for off- and on-times. QDs were immobilized on silicon oxide surfaces with varying grades of hydroxylation and silanol group densities, respectively. While the off-time distributions remain unaffected by changing the surface properties of the silicon oxide, a deviation from the power law dependence is observed in the case of on-times. This deviation can be described by a superimposed single exponential function and depends critically on the local silanol group density. Furthermore, QDs in close proximity to silanol groups exhibit both high average photoluminescence intensities and large on-time fractions. The effect is attributed to an interaction between the QDs and the silanol groups which creates new or deepens already existing hole trap states within the ZnS shell. This interpretation is consistent with the trapping model introduced by Verberk et al. (R. Verberk, A. M. van Oijen and M. Orrit, Phys. Rev. B, 2002, 66, 233202).

Blinking dynamics of CdSe/ZnS semiconductor quantum dots (QD) are characterized by (truncated) power law distributions exhibiting a wide dynamic range in probability densities and time scales both for off- and on-times. QDs were immobilized on silicon oxide surfaces with varying grades of hydroxylation and silanol group densities, respectively. While the off-time distributions remain unaffected by changing the surface properties of the silicon oxide, a deviation from the power law dependence is observed in the case of on-times. This deviation can be described by a superimposed single exponential function and depends critically on the local silanol group density. Furthermore, QDs in close proximity to silanol groups exhibit both high average photoluminescence intensities and large on-time fractions. The effect is attributed to an interaction between the QDs and the silanol groups which creates new or deepens already existing hole trap states within the ZnS shell. This interpretation is consistent with the trapping model introduced by Verberk et al. (R. Verberk, A. M. van Oijen and M. Orrit, Phys. Rev. B, 2002, 66, 233202).