Automated application of drift correction to sample studied under electron microscope
Methods and systems for calibrating a transmission electron microscope are disclosed. A fiducial mark on the sample holder is used to identify known reference points so that a current collection area and a through-hole on the sample holder can be located. A plurality of beam current and beam area measurements are taken, and calibration tables are extrapolated from the measurements for a full range of microscope parameters. The calibration tables are then used to determine electron dose of a sample during an experiment at a given configuration.
1 . A method for measuring electron dose in a sample with a transmission electron microscope (TEM), the method comprising:
locating a fiducial mark on a TEM holder tip, wherein the TEM holder tip includes a through-hole located at a predetermined distance from the fiducial mark and a current collection area located at a predetermined distance from the fiducial mark;
calibrating the TEM for measuring beam area across a range of possible beam areas using the located fiducial mark;
calibrating the TEM for measuring beam current across a range of possible beam currents using the located fiducial mark;
measuring electron dose on the sample during an experiment using the calibrated TEM; and
reducing an electron dose rate when a critical value for an electron dose rate or a cumulative electron dose has been reached.
2 . The method of claim 1 , further comprising generating a heatmap of the sample showing the measured electron dose for each X-Y coordinate of the sample.
3 . The method of claim 2 , wherein the heatmap of the sample includes both an electron dose rate and a cumulative electron dose for each X-Y coordinate of the sample.
4 . The method of claim 1 , further comprising generating an alert when the electron dose rate or cumulative electron dose is approaching the critical value.
5 . The method of claim 1 , further comprising jogging a stage to adjust a position of the TEM and taking additional beam current measurements to determine where the TEM is centered above the current collection area.
6 . The method of claim 1 , further comprising converting the measured electron dose and measurements of beam area to generate electron interaction volume data in three dimensions.
7 . The method of claim 1 , wherein the electron dose rate is reduced by changing an aperture setting, changing the spot size, changing a beam intensity, or changing the beam current.
8 . A microscope control system for measuring electron dose in a sample with a transmission electron microscope (TEM), the system comprising:
one or more hardware processors configured for:
locating a fiducial mark on a TEM holder tip, wherein the TEM holder tip includes a through-hole located at a predetermined distance from the fiducial mark and a current collection area located at a predetermined distance from the fiducial mark;
calibrating the TEM for measuring beam area across a range of possible beam areas using the located fiducial mark;
calibrating the TEM for measuring beam current across a range of possible beam currents using the located fiducial mark;
measuring electron dose on the sample during an experiment using the calibrated TEM; and
reducing an electron dose rate when a critical value for the electron dose rate or a cumulative electron dose has been reached.
9 . The microscope control system of claim 8 , wherein the one or more hardware processors are further configured for generating a heatmap of the sample showing the measured electron dose for each X-Y coordinate of the sample.
10 . The microscope control system of claim 9 , wherein the heatmap of the sample includes both the electron dose rate and the cumulative electron dose for each X-Y coordinate of the sample.
11 . The microscope control system of claim 8 , wherein the one or more hardware processors are further configured for generating an alert when the electron dose rate or cumulative electron dose is approaching the critical value.
12 . The microscope control system of claim 8 , wherein a stage is jogged to adjust a position of the TEM, and wherein additional beam current measurements at each adjusted position to determine where the TEM is centered above the current collection area.
13 . The microscope control system of claim 8 , wherein the one or more hardware processors are further configured for converting the measured electron dose and measurements of beam area to generate electron interaction volume data in three dimensions.
14 . The microscope control system of claim 8 , wherein the electron dose rate is reduced by changing an aperture setting, changing the spot size, changing a beam intensity, or changing the beam current.
15 . A microscope control system for measuring electron dose in a sample with a transmission electron microscope (TEM), the system comprising:
one or more hardware processors configured for:
locating a fiducial mark on a TEM holder tip, wherein the TEM holder tip includes a through-hole located at a predetermined distance from the fiducial mark and a current collection area located at a predetermined distance from the fiducial mark;
calibrating the TEM for measuring beam area across a range of possible beam areas using the located fiducial mark;
calibrating the TEM for measuring beam current across a range of possible beam currents using the located fiducial mark;
measuring electron dose on the sample for a plurality of positions on the sample during an experiment using the calibrated TEM; and
generating and displaying a heatmap of the sample showing the measured electron dose for X-Y coordinates for the plurality of positions on the sample.
16 . The microscope control system of claim 15 , wherein the heatmap of the sample includes both an electron dose rate and a cumulative electron dose for the X-Y coordinates for the plurality of positions on the sample.
17 . The microscope control system of claim 15 , wherein the one or more hardware processors are further configured for generating a warning when the electron dose for a particular position on the sample exceeds a threshold value.
18 . The microscope control system of claim 15 , wherein the one or more hardware processors are further configured for generating a matrix of conditions for adjusting the electron dose or the electron dose rate on the sample.
19 . The microscope control system of claim 15 , wherein the one or more hardware processors are further configured for automatically adjusting a spot size, an intensity, or a position of an electron beam when the electron dose for a particular position on the sample exceeds a threshold value.
20 . The microscope control system of claim 15 , wherein the heatmap of the sample adjusts automatically as a magnification of the TEM is adjusted.