Detection of hot electron current with scanning hot electron microscopy

Abstract

Scanning hot electron microscopy (SHEM) has been proposed as an experimental technique which allows for detection of hot electrons emitted from a subsurface semiconductor structure, thus making it possible to obtain the spatial distribution of hot electrons in a device. Here we present the experimental evidence of SHEM operation. Hot electrons with energies of 3 eV are injected by means of a Si/CaF2/Au heterostructure and subsequently detected at the tip of a scanning tunneling microscope in the SHEM configuration. The measured hot electron current was approximately 4 pA for a tunnel current of 5 nA. These results, although still of a preliminary nature, show the potential of SHEM as a technique suitable for the visualization of electron wave effects in semiconductor structures.

Shortening of Detection Time for Observation of Hot Electron Spatial Distribution by Scanning Hot Electron Microscopy

“…Accordingly, the vibrational noise can be sufficiently smaller than the HE current of 5 pA reported in ref. 7.…”

“…The sample structure and fabrication process are the same as for the described previously. 7) The SHEM was made by modifying a Nanoscope II. The tip material was Pt-Ir.…”

“…6) Furthermore, a hot electron (HE) in a solid was observed by SHEM. 7) However, it took 600 s to detect the HE for a data point. To observe the spatial distribution without thermal drift, the detection time of the HE must be reduced.…”

Metal–insulator–semiconductor emitter with an epitaxial CaF2 layer as the insulator

“…7 The difference between the SHEM and the vacuum emitter cases is the applied voltage; the applied voltage for SHEM was 3 V, whereas a higher voltage than the work function of gold ͑5.4 eV͒ must be used in the vacuum emitter case. The semiconductor is silicon because CaF 2 can be epitaxially growth on a Si substrate.…”

Theoretical Relation between Spatial Resolution and Efficiency of Detection in Scanning Hot Electron Microscope

“…1) The SHEM can visualize the quantum interference and diffraction patterns of a HE wave in a solid. After the first demonstration of the HE detection using a scanning probe, 2) the noise properties were investigated to reduce the detection time, that is, the integration time for the phase-sensitive detection. 3) The spatial resolution of the SHEM was estimated by a one-dimensional (1D) analysis of the electrostatic potential between the tip and the sample surface.…”