Observations of Si field evaporation

Area of Science:

• Materials Science
• Surface Science
• Nanotechnology

Background:

• Field evaporation is crucial for atom probe tomography (APT) analysis of materials.
• Understanding silicon (Si) field evaporation is essential for its application in microelectronics and nanotechnology.
• Previous studies have explored Si evaporation, but detailed characterization under varying conditions remains important.

Purpose of the Study:

• To investigate the field evaporation behavior of crystalline <100> silicon using a 3D atom probe.
• To determine the influence of temperature, substrate doping, and evaporation modes on Si field evaporation.
• To assess the impact of different evaporation modes on mass resolution in APT.

Main Methods:

• Utilized a 3D atom probe with a local electrode geometry for field evaporation studies.
• Investigated crystalline <100> Si samples with varying substrate doping (up to 10 Ohm cm).
• Analyzed evaporation rates and mass spectra across a temperature range of 40-150K and pulse fractions (pf) from 5% to 30%.

Main Results:

• Si field evaporation rates showed no temperature dependence below 110K but an exponential dependence above 110K.
• Evaporation rates were independent of substrate doping up to 10 Ohm cm between 40-150K.
• Two distinct evaporation modes were observed: one with ~1at% H+ in the mass spectrum and another with negligible H.
• Operation in the H+-associated mode degraded mass resolution by up to 80% for 10 Ohm cm Si samples as pf increased.
• No mass resolution loss was observed for ~0.001 Ohm cm Si samples over the studied pf range.

Conclusions:

• Crystalline silicon field evaporation is strongly influenced by temperature above 110K.
• The presence of hydrogen during field evaporation significantly impacts mass resolution, particularly for doped silicon.
• Careful control of evaporation modes and experimental conditions is critical for accurate APT analysis of silicon.