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William Wood edited this page Jan 15, 2021 · 3 revisions

Quick Usage Guide

Contents

  1. Introduction
  2. Start-Up
  3. Setting-Up Measurements
  4. Measurement Sweeps
  5. Running Measurements
  6. Viewing Results
  7. Analysing Results

Setting-Up Measurements

After starting-up successfully, you will be presented with the "Measurement" page.

On the left you will see the "Measurement Parameters" panel. Here you can tell FetCh:

  • The name of your device/set of measurement
  • Where to output measurements result to
  • The dimensions and dielectric details of your device

In our example we have told FetCh:

  • These measurements should be called "DeviceName"
  • These measurements should output to "/home/william/Desktop" (i.e. the Desktop folder)
  • Our device is 420um x 105um x 40nm in size with a four-point probe separation of 140um
  • The dielectric layer on our device is CYTOP and is 400nm thick

On the right is the Measurement Queue. This where you can queue-up measurements to run sequentially, allowing you to design your own measurement sequences. Currently, there are no measurements queued, hence the list is empty:

By clicking the "Add" button, we will get a drop-down menu of possible measurements, actions and sweeps to add to the queue, like so:

Options under "Measurements" are each a single measurement (i.e. an action that produces data), like Conductivity measurements, Output Curves etc. Those under "Actions" are are actions that produce no data, for instance changing temperature or waiting for a specified amount of time. The options under "Sweeps" are special kinds of loops that will repeat whichever measurements/actions you want for different values of something. For instance, "Temperature Sweep" will allow you to repeat a set of measurements/actions at multiple different temperatures.

For our example, let's say we want to measure the conductivity of our device. To do this, we should add a "Conductivity" measurement to the queue:

Doing so will open a window that lets us configure the conductivity measurement. Notice that this window has two tabs: "Parameters" and "Instruments":

Parameters

Here you set the measurement parameters. These normally consist of things like integration and delay times as well as current/voltage values to use in the measurement.

For our example of Conductivity, these are:

  • Integration time
  • Delay time
  • First value in current sweep
  • Last value in current sweep
  • Number of steps in current sweep
  • Whether the sweep should go both ways
  • Whether a gate voltage should be applied during the measurement

Let's say we want to sweep from -50uA to +50uA in 25 steps, waiting 500ms after setting each current value before measuring (ie a 500ms delay time). Therefore, we enter -50x10^-6 and +50x10-6 in the "Start [A]" and "Stop [A]" fields respectively, 25 in the "No. Steps" field and 500x10^-3 into the "Delay Time [s]" field like above.

Instruments

Here you choose which instruments and channels on those instruments to use for specific purposes in the measurement. For instance, you will often need to select which SMU channel to use as the Source-Drain channel or, if you're using an SPA, which channel is Ground/Source and which channel is Drain.

In our example of conductivity, we can choose instruments to be:

  • Ground (for SPAs, otherwise optional)
  • Source-Drain Channel (required)
  • Source-Gate Channel (only required if applying a gate voltage)
  • Four-Point Probe Channel 1 (optional)
  • Four-Point Probe Channel 2 (optional)

For our example, we want to perform a four-point probe conductivity measurement using the four-point measurement functionality of our connected SMU named "SMU 1". Our SMU also has multiple channels, and our set-up is connected such that "Channel 2" is the one being used. Therefore, we select "SMU 1" in the "Source-Drain Channel" panel then select "Channel 2" in the channel selection and then tick the "Four Point Probe" option.

FetCh will figure out how best to perform the measurement with the instruments you configure. So in our case, it will perform a four-point probe conductivity measurement using the four-point probe functionality of the SMU we've configured to be used as the Source-Drain channel. If we had, for instance, configured a separate SMU channel or other voltmeter to be one of the "Four-Point Probe" channels, then it would perform a four-point probe conductivity measurement using the current set by the Source-Drain SMU and the voltage measured by the Four-Point Probe SMU/Voltmeter.

Adding to Queue

When you press "OK" the measurement will be added to the queue. You can edit any of the parameters after adding it to the queue by double-clicking on it in the queue which will re-open the configuration window. Repeat this process to add all the measurements you want to perform to the queue:

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