BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Sabre//Sabre VObject 4.6.0//EN CALSCALE:GREGORIAN BEGIN:VTIMEZONE TZID:Europe/Zurich X-LIC-LOCATION:Europe/Zurich TZURL:http://tzurl.org/zoneinfo/Europe/Zurich BEGIN:DAYLIGHT TZOFFSETFROM:+0100 TZOFFSETTO:+0200 TZNAME:CEST DTSTART:19810329T020000 RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:+0200 TZOFFSETTO:+0100 TZNAME:CET DTSTART:19961027T030000 RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU END:STANDARD END:VTIMEZONE BEGIN:VEVENT UID:news1052@physik.unibas.ch DTSTAMP;TZID=Europe/Zurich:20260728T075935 DTSTART;TZID=Europe/Zurich:20260731T110000 SUMMARY:Variable-Frequency and Quantitative Capacitance Measurements by Dua l-Bias Modulation Electrostatic Force Microscopy DESCRIPTION:Atomic force microscopy (AFM) enables the characterization of v arious sample properties through local force detection. Electrostatic forc es acting between the tip and sample can also be measured using AFM\, an a pproach known as electrostatic force microscopy (EFM). In conventional EFM \, the DC component or a specific frequency component of the electrostatic force is detected to investigate the surface potential and electrical tip –sample capacitance. However\, the frequency range accessible to EFM is severely limited by the narrow bandwidth of conventional force-detection m ethods\, such as amplitude-modulation (AM) and frequency-modulation (FM) t echniques. Furthermore\, in FM-EFM\, the cantilever frequency shift induce d by the electrostatic force is proportional to the force gradient\, makin g it difficult to quantitatively determine the tip–sample capacitance fr om the measured frequency shift.\\r\\nTo overcome these limitations\, we h ave developed dual-bias modulation EFM (DEFM)\, which enables capacitance measurements over a wide frequency range as well as quantitative evaluatio n of the capacitance. In DEFM\, two AC voltages are applied between the ti p and sample\, and the electrostatic-force component at their difference f requency is detected using a lock-in amplifier. The two AC frequencies can be varied while keeping their difference frequency constant. This scheme enables measurement of the frequency-dependent capacitance associated with deep-level states in semiconductors. In addition\, we have analytically d erived a formula for quantitatively determining the tip–sample capacitan ce\, including the semiconductor capacitance\, from the measured cantileve r frequency shift.\\r\\nIn this talk\, we demonstrate the capabilities and practical applicability of DEFM through measurements of Cu(In\,Ga)(Se\,S) ₂ photovoltaic materials and metal–oxide–semiconductor structures. X-ALT-DESC:

Atomic force microscopy (AFM) enables the characterization of various sample properties through local force detection. Electrostatic fo rces acting between the tip and sample can also be measured using AFM\, an approach known as electrostatic force microscopy (EFM). In conventional E FM\, the DC component or a specific frequency component of the electrostat ic force is detected to investigate the surface potential and electrical t ip–sample capacitance. However\, the frequency range accessible to EFM i s severely limited by the narrow bandwidth of conventional force-detection methods\, such as amplitude-modulation (AM) and frequency-modulation (FM) techniques. Furthermore\, in FM-EFM\, the cantilever frequency shift indu ced by the electrostatic force is proportional to the force gradient\, mak ing it difficult to quantitatively determine the tip–sample capacitance from the measured frequency shift.

\n

To overcome these limitations\, we have developed dual-bias modulation EFM (DEFM)\, which enables capacit ance measurements over a wide frequency range as well as quantitative eval uation of the capacitance. In DEFM\, two AC voltages are applied between t he tip and sample\, and the electrostatic-force component at their differe nce frequency is detected using a lock-in amplifier. The two AC frequencie s can be varied while keeping their difference frequency constant. This sc heme enables measurement of the frequency-dependent capacitance associated with deep-level states in semiconductors. In addition\, we have analytica lly derived a formula for quantitatively determining the tip–sample capa citance\, including the semiconductor capacitance\, from the measured cant ilever frequency shift.

\n

In this talk\, we demonstrate the capabili ties and practical applicability of DEFM through measurements of Cu(In\,Ga )(Se\,S)₂ photovoltaic materials and metal–oxide–semiconductor struc tures.

END:VEVENT END:VCALENDAR