Material Analysis - Ultrafast AFM

Research Interests

  • 2D materials
  • Thin film molecule samples
  • Defects

Motivation

Understanding the fundamental properties of nanomaterials has potential applications in areas including solar cell devices and molecular materials.

Ultrafast AFM

The Ultrafast AFM technique was first developed in our group by Schumacher et al. in 2017 by combining an ultrafast laser with non-contact AFM. When the laser impinges on the sample, it generates a photoinduced sample response, which is then detected as a force by the AFM tip. The temporal resolution of this technique is afforded by the ultrafast laser, and reaches the femtosecond regime. The spatial resolution is afforded by the sharpness of the AFM probe, and reaches the nanometer regime. This unique combination of spatial and temporal resolution will allow us to characterize local recombination rates and carrier decay times in photovoltaic materials.

Ultra-High Vacuum System

The centerpiece of the atomic manipulation facility is a custom built JEOL JSPM-4500A ultrahigh vacuum, low temperature, surface science system. This instrument consists of several standard surface science tools, along with an AFM (atomic force microscope), an STM (scanning tunneling microscope) and an FE-SEM (field emission-secondary electron microscope) which allows the AFM or STM tip to be accurately positioned over regions of interest on a sample.

We have recently modified the JEOL system for ultrafast AFM by incorporating:
  • Two ultrafast FemptoFiber Pro ultrafast lasers (one is centered in the near-infrared at 780 nm with 100 fs pulses, and the other is a tunable visible laser with 400 fs pulses).
  • Zurich Instruments UHF Lock-in amplifier.
  • A piezo-controlled optical mirror in UHV to steer the laser beam onto the sample.

General

  • Three chamber ultrahigh vacuum system: quick load lock chamber, specimen treatment chamber, analysis chamber
  • Base pressure in treatment and analysis chambers less than 10e-8 Pa

Specimen Treatment Chamber

  • LEED/Auger spectrometer
  • Four-source e-beam evaporator for the deposition of metals
  • Three source evaporator for the deposition of organic molecules
  • Quartz crystal deposition monitor for determining thickness of evaporated films
  • Ion gun
  • Specimen cleaving device
  • In situ mask system for depositing macroscopic electrode patterns (designed in-house)

Analysis Chamber

  • AFM: frequency modulated atomic force microscopy (NC-AFM), contact mode, tapping mode, magnetic force microscopy, electric force microscopy, Kelvin force microscopy, friction force microscopy, phase detection, current image
  • STM: I-V, S-V, I-S, CITS
  • Field emission SEM, designed for observing tip and/or sample on SPM stage.
  • Imaging can be performed at temperatures ranging from 30 K to 800 K
  • Nanonis SPM Control System with dual PLL
  • Ultrafast AFM

People

Group Members

  • Andreas Spielhofer (PhD student)
  • Megan Cowie (PhD student)
  • Rikke Plougmann (PhD student)

Former Group Members

Collaborators

Recent publications