# Aloof Electron Probing of In-Plane Surface Photovoltaic Charge Distributions on GaAs Surfaces

## TL;DR

This paper shows how laser light can create electric fields on a semiconductor surface that steer electrons in a vacuum, allowing for new ways to control electron beams.

## Contribution

The study introduces aloof electron probing as a novel method to map and manipulate surface photovoltaic charge distributions on GaAs surfaces.

## Key findings

- Aloof electrons are strongly deflected by electric fields from SPV charges on GaAs surfaces.
- The SPV charge distribution remains detectable for over 1 second after laser exposure.
- The electric field from SPV extends up to 100 micrometers into the vacuum.

## Abstract

The motion of free electrons moving parallel and above
a semiconductor
surface can be influenced by shining a laser light onto the surface.
Here we report strong deflection of aloof electrons by an undoped
GaAs surface illuminated with a 633 nm laser. The deflecting electric
field from the surface photovoltaic charges extends 100 μm into
the vacuum. As surface photovoltage (SPV) is sensitive to the electronic
states of the GaAs surface, the aloof electron beam serves as a probe
for SPV charge dynamics on the mesoscopic length scale. The observed
in-plane SPV charge distribution persists beyond 1 second after the
laser beam is blocked. Our work suggests the possibility of writing
designed 2D charge patterns on semiconductor surfaces with a scanning
laser beam, providing unusual flexibility for electron beam manipulation.