We identify fundamental mechanisms of electron escape from self-organized InAs quantum dots ͑QD's͒ in a vertical electric field by time-resolved capacitance spectroscopy. Direct tunneling and a thermally activated escape process are observed. The QD electron ground and first-excited states are concluded to be located ϳ190 and ϳ96 meV below the GaAs matrix conduction band, respectively. Our experimental results and their interpretation are in good agreement with eight-band k•p calculations and demonstrate the importance of tunnel processes.

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Switching properties of selfassembled ferroelectric memory cells" (1999). Alexei Gruverman Publications. 5.

Wetting of the pore walls of porous templates is a simple and convenient method to prepare nanoshell tubes. Wafer-scale fabrication of ferroelectric lead zirconate titanate and barium titanate nanoshell tubes was accomplished by wetting porous silicon templates with polymeric precursors. The ferro- and piezoelectric properties of an individual ferroelectric nanoshell tube either of PZT or of BaTiO3 were electrically characterized by measuring the local piezoelectric hysteresis. A sharp switching at the coercive voltage of about 2 V was shown from the hysteresis loop. The corresponding effective remnant piezoelectric coefficient is about 90 pm/V. We have also prepared highly ordered arrays of free-standing ferroelectric nanoshell tubes obtained by partial etching of the silicon template. Such materials might be used as building blocks of miniaturized devices and could have a significant impact in the field of nano-electromechanical systems.

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