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1

KFM calibration method

Jabłoński R., Ligowski M., Tabe M.

Elektronika : konstrukcje, technologie, zastosowania

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2013

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Vol. 54, nr 6

19-21

PL

Istnieje wiele sposobów kalibracji kelvinowskiego mikroskopu sił atomowych (Kelvin Probe Force Microscope, KFM) [1], a uzyskane dokładności zależą od wybranej metody. W publikacji przedstawiona jest nowa metoda wzorcowania KFM. Metoda jest oparta na pomiarze potencjału powierzchniowego wzorca odniesienia i porównaniu wyniku z uzyskanym za pomocą KFM. Pozwala ona na wzorcowanie w całym zakresie pomiarowym mikroskopu zarówno w wartościach bezwzględnych jak i dynamicznie zmiennych. Napięcie powierzchniowe wzorca odniesienia użytego do wzorcowania jest regulowane w zależności od potrzeb (nie jest więc zdefiniowane jego fizycznymi parametrami). Stosując tą metodę zarówno charakterystyka czasowa jak i dokładność pomiaru mogą być regulowane przez właściwe ustawienie kontrolera PI i wzmacniacza Lock-In. Okazało się, że przy wzroście wzmocnienia proporcjonalnego, zmniejsza się zakres pomiarowy przy jednoczesnym zwiększeniu rozdzielczości. Metoda została zastosowana do wzorcowania niskotemperaturowego mikroskopu KFM. Osiągnięte wyniki potwierdzają, że KFM może mierzyć potencjał w zakresie -3...3 V. Obliczone odchylenie standardowe dla każdego punktu kalibracyjnego wynosiło mniej niż 15 mV. Biorąc pod uwagę także błąd systematyczny można skonkludować że niepewność w całym zakresie pomiarowym wynosi 20 mV.

EN

There are many possible ways to calibrate the Kelvin Probe Force Microscope [1] and various accuracy levels can be achieved accordingly to employed method. The paper presents novel method for calibrating Kelvin Probe Force Microscope. The method is based on measuring the surface potential of a reference sample and comparing it with the results obtained by KFM. It offers a calibration possibility in the whole measuring range of the microscope both in terms of absolute values and dynamic behavior. The surface potential of a reference sample used for calibration is adjusted according to needs (instead of being defined by physical parameters of the sample). Using this method both the time characteristics and the measurement accuracy can be adjusted by a proper setting of PI controller and Lock-In amplifier gains. In particular, with a higher proportional gain the measuring range is decreased but obtained resolution is increased. The method has been applied for the calibration of Unisoku Low Temperature KFM. Obtained results proves that KFM can measure the potential within the -3...3 V. The calculated standard deviation for each calibration point is less than 15 mV. Taking into consideration also systematic error it can be concluded, that the uncertainty in a whole measuring range is 20 mV.

2

Single-electron transport characteristics in quantum dot arrays due to ionized dopants

Moraru D., Ligowski M., Tarido J. C., Miki S., Nakamura R., Yokoi K., Mizuno T., Tabe M.

Journal of Automation Mobile Robotics and Intelligent Systems

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2009

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Vol. 3, No. 4

52-54

EN

Single charge manipulation for useful electronic functionalities has become an exciting and fast-paced direction of research in recent years. In structures with dimensions below about 100 nm, the physics governing the device operation turn out to be strikingly different than in the case of larger devices. The presence of even a single charge may completely suppress current flow due to the basic electronelectron repulsion (so called Coulomb blockade effect) [1]. It is even more exciting to control this effect at the level of single-electron/single-atom interaction. The atomic entity can be one donor present in silicon lattice with a Coulombic potential well. In principle, it can accommodate basically a single electron. We study the electrical behavior of nanoscale-channel silicon-on-insulator field-effect transistors (SOI-FETs) that contain a discrete arrangement of donors. The donors can be utilized as "stepping stones" for the transfer of single charges. This ability opens the doors to a rich world of applications based on the simple interplay of single charges and single atoms, while still utilizing mostly conventional and well established fabrication techniques. In this work, we distinguish the effects of single-electron transport mediated by one or few dopants only. Furthermore, we show how the single-electron/single-donor interaction can be tuned by using the external biases. We demonstrate then by simulation and experiment the feasibility of single-electron/bit transfer operation (single-electron turnstile).

3

Detection of individual dopants in singe-electron devices - a study by KFM observation and simulation

Ligowski M., Moraru D., Miftahul A., Tarido J. C., Mizuno T., Tabe M., Jabłoński R.

Journal of Automation Mobile Robotics and Intelligent Systems

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2009

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Vol. 3, No. 4

130-133

EN

Single electron devices (SEDs) are candidates to become a keystone of future electronics. They are very attractive due to low power consumption, small size or high operating speed. It is even possible to assure compatibility with present CMOS technology when natural potential fluctuations introduced by dopant atoms are used to create quantum dots (QD). However, the main problem of this approach is due to the randomness of dopant distribution which is characteristic for conventional doping techniques. This leads to scattered characteristics of the devices, which precludes from using them in the circuits. In these work we approach the problem of correlating the distribution of QD's with the device characteristics. For that, we investigate with a Kelvin probe force microscope (KFM) the surface potential of Si nanodevice channel in order to understand the potential landscape. Results reveal the features ascribable to individual dopants. These findings are supported also by simulation results.