Development of a Quantitative Electrostatic Force Microscope

California Institute Of Technology, Pasadena CA

Investigators

Abstract

0076486 Atwater This grant will help develop quantitative electrostatic force scanning probe microscopy. The project includes modification of a commercial ultrahigh vacuum scanning probe microscope and development of new electrostatic force microscopy simulation software. The program comprised both ultrahigh vacuum electrostatic force microscopy measurements and development and testing of finite element electrostatic simulation software describing tip-sample interactions, including van der Waals and electrostatic force contributions . This will enable more quantitative understanding of nanometer-scale charge distributions and low mobility electronic transport. The immediate scientific use for the instrument will be in a collaborative Caltech/Bell Labs/NASA-JPL multi-investigator research program aimed at probing charge injection and storage in silicon nanoparticle structures for nonvolatile memory applications. Information and software needed to perform quantitative EFM will be disseminated to the materials research community. Electrically insulating thin films are critical and ubiquitous components of electronic devices such as integrated circuits and micromechanical devices. Trapping of electronic charge, whether by design or as an unintended effect, is a common characteristic of insulating thin films. It is desirable to be able to quantitatively measure the extent of and mechanisms for charge trapping in order to better understand the performance and reliability of insulating thin films. Scanning probe microscope techniques such as electrostatic force microscopy have opened a new vista in the understanding charge trapping in insulators because they enable measurement at nanometer-scale spatial resolution and total charge sensitivity down to the single electron level. To date, such electrostatic force microscopy measurements have been used as a qualitative but not a quantitative tool for understanding charge trapping in insulators. This project aims to put the electrostatic force microscopy method on a firm quantitative foundation, through a combination of measurements and development of simulation software needed for quantitative understanding. The results will be applied to characterize charge trapping in nonvolatile floating gate memory device materials containing semiconductor nanocrystals. These materials and the devices made with them are very promising candidates for the next-generation of ultradense, low-power nonvolatile "flash" memory chips like those now used widely in portable electronic devices such as wireless telephones, pagers, electronic cameras and personal digital assistants.