For a metallic surface (Au) and highly doped (N) and (P) semiconductor surfaces (GaInAs) and for localised zones (2 Â 2 mm) we have measured using an electrostatic force microscope the variation of the gradient of the electrostatic force by the signal (phase of the oscillating movement of the metallised tip) as a function of the sample-tip potential difference (À 4 V to 4 V). In both cases the signal shows a quadratic variation with the sample-tip potential difference. The variation of the signal is of the order of magnitude of the theoretical predictions obtained by modelling the shape of the tip by a truncated cone a portion of a sphere.Using the parabolic curve that ®ts the experimental results, the value of the contact potential difference, corresponding to a zero value of the electrostatic force gradient, can be determined with an accuracy of 50 mV. The contact potential difference, measured between the metallised tip and the metal (Au), taken as a reference, allows the work function of the metal tip to be determined (5.25 eV). The values of the contact potential difference for the GaInAs (N) and (P) surfaces can be explained by the Fermi level pinning due to surface charges.The electrostatic force microscope (EFM) which is derived from the atomic force microscope (AFM) is sensitive to the electrostatic force between the metallised tip and the sample. This electrostatic force can be due to the presence of existing charges or to an applied bias between the tip and the sample.The interest of this new microscopy is its ability to image local voltages of working microelectronic structures [1, 2], charges on insulator surfaces [3] and to image the ferroelectric domains [4].The curve of the electrostatic force versus the potential difference between the tip and the sample allows measurement of the contact potential difference which is directly related to the work function difference. As for the Kelvin method [5], this also allows local potentiometry to be performed [6], or the dopant distribution to be mapped [7].The electrostatic force due to the effect of a potential difference between the tip and the surface of a metal or a highly doped semiconductor can be evaluated by an analytical model using a geometrical simulation of the tip shape and the cantilever [8,9].In this paper, we have used an EFM working in thè`t apping'' mode. The electrostatic force is separated from the van der Waals force by using a``lift'' method which allows ®rst the topography to be recorded using the van der Waals forces and then the surface topography to be followed at a distance constant equal or greater to 100 nm. At this distance, the tip is only sensitive to the electrostatic force.In the case of a metallic surface and of a highly doped semiconductor, we have calculated, using the geometrical shape of the tip, the electrostatic force as well as its gradient with the distance. We have done experiments by applying a bias to the Au contacts and the GaInAs (N) and (P) layers with the metallised tip grounded. For each sample, a 2 Â 2 mm ...

No abstract

This supplement of Mikrochimica Acta contains selected papers from the Fourth Workshop of the European Microanalysis Society (EMAS) on "Modern Developments and Applications in Microbeam Analysis" which took place in May 1995 in Saint Malo (France).EMAS was founded in 1986 by members from almost all european countries in order to stimulate research, applications and development of all forms of microbeam methods. One important EMAS activity is the organisation of biennial workshops for demonstrating the current status and developing trends of microanalytical techniques. For this meeting, EMAS chose to highlight the following topics: Monte-Carlo simulations, transport calculations and use of soft X-rays for electron probe microanalysis (EPMA), dynamic secondary ion mass spectrometry (SIMS), detection of small quantities using different techniques: synchrotron radiation X-ray fluorescence, particle induced X-ray emission (PIXE), cathodoluminescence microscopy (CL). Two new kinds of instrumental techniques were also presented: atomic probe and scanning probe microscopy (STM). The aim of the conference is to give introductory lectures corresponding to the topics of the meeting and to have contributions in the form of poster sessions. More than 80 posters were presented. Most of them gave a short oral presentation. The poster subjects were related to the use of microanalytical techniques: EPMA with wavelength dispersive spectrometry (WDS) and energy dispersive spectrometry (EDS), Auger electron spectrometry (AES), secondary ion mass spectrometry (SIMS), scanning electron microscopy and other topographical methods like scanning tunneling microscopy (STM) or atomic force microscopy (AFM). The field of applications is very broad: metallurgy, mineralogy, semiconductor, ceramic, glass, composite, polymer and biological material.The authors originate from almost all european countries, including eastern european ones and Russia. One invited lecture was given by a USA speaker.This issue contains the full texts of the ten introductory lectures and 50 brief articles. These articles are the condensed scientific informations of the poster sessions. They were subjected to peer-review according to the usual procedure and some of them were rejected.Proceedings of previous EMAS workshops were also published, either as a supplement to or in a regular issue of Mikrochimica Acta. We hope that these contributions to the field of microbeam techniques will be found to be useful.