README.md

Origin-Scripts

This repository contains LabTalk Scripts for automated data analysis of organic field-effect transistor (OFET) and electrolyte-gated organic field-effect transistor (EG-OFET) data. The scripts are compatible with Origin 2018 Pro or newer.

For these scripts to work:

• The data files need to have a certain internal structure, otherwise the scripts will not work properly. See the Script examples project file for examples. If the data were acquired using the Agilent-415X LabVIEW programs, then the scripts will work.
• The data filenames have to be in a certain format. If the format is different the scripts will not work. See the Data filenames section for details. Alternatively, look at the Script examples project file and save your experimental data accordingly.
• The graph templates that the scripts use to plot the data have to have filenames in a certain format. If the format is different, or if the template does not exist, a generic template will be used but the scripts will work.

Installation

To install the scripts, perform the following steps:

1. Copy the Scripts folder to C:\Users\<Account Name>\Documents\OriginLab.
   • The <Account Name> is the name of your user account in your PC.
   • The filepath should NOT contain spaces!
   • The filenames of the scripts should also NOT contain dashes (-), as Origin cannot handle them.
2. Copy the Themes and Templates folders to C:\Users\<Account Name>\Documents\OriginLab\User Files.
   • These folders contain the graph themes and templates.
   • In this case, there is no issue with spaces being in the filepath.
3. Copy the project files in the Examples folder into a folder of your choice.
   • The Script examples project file contains separate folders, each of whom tests a particular script. Each of these scripts only processes files that exist in the same folder as the script. All the scripts are tested in this file, except the Experiment comparison scripts.
   • The Script examples - Experiment comparison project file is only designed to test the Experiment comparison scripts, which compare experimental data between different EG-OFET experiments (and hence from different folders).
4. Run OriginLab and open the Script examples project file.
   • Each folder contains sample data and a readme file. The readme provides instructions on how to test the corresponding Origin script mentioned in the folder name.
5. Open the Library script with CodeBuilder and modify the templatepath$ string variable at the top of the script, so that it points to the Templates folder in your PC. Make sure to save the script.
   • The Library is a script that contains functions that other scripts call. It will not meant to be executed by itself.
6. Select View and then Command Window. The Command Window will appear. It is similar to the Linux command line and allows one to give commands directly to Origin, and run scripts.
7. In the Command Window, write cd C:\Users\<Account Name>\Documents\OriginLab\Scripts; to set the Scripts directory as the working directory (do not forget the semicolon!). Then press ENTER.
8. Now the scripts should work. To verify this, start typing the name of a script in the Command Window (e.g. EG) and then press TAB. If the working directory has been set correctly, Origin will try to autocomplete the partially typed script name with one of the EG-OFET scripts.
9. Test a script by going to a folder of the Script examples project file, and following the instructions in the readme file. To run a script, type the name of the script in the Command Window and press ENTER.

Data filenames

Fields and their Values

As mentioned earlier, the scripts expect to see data filenames in a certain format. Each filename consists of different fields, separated by an underscore (_). The different values for each of the different fields can be seen in the Library file.

• Depending on the type of measurement, each filename will contain different fields. The Filename formats section presents the different file formats for each type of measurement.
• When a script is executed, the data filename is parsed and the values of the different fields are used to select the appropriate graph template, as well as to calculate different performance metrics (e.g., mobility).

The different fields are:

• batchNo: The number of the batch (e.g. 235th).
• Architecture: The architecture of the device (e.g. TGBC-OFET, TGBC-EG-OFET).
• material: The semiconductor used to make the FET (e.g. IDTBT, C14-PBTTT).
• concentration(No-units): The concentration of the material/semiconductor (e.g. 10-gl means 10 g/L).
• material: The semiconductor used to make the FET (e.g. IDTBT, C14-PBTTT).
• solvent: The solvent(s) used to make the semiconductor solution (e.g. 100pDCB, 75pDCB-25pCF).
• annealing: The annealing conditions of the semiconductor thin films (e.g. 100C-1h).
• additive: The additives or self-assembled monolayers (SAMs) used in the FET (e.g. Pristine, TCNQ-40-nm).
  • For evaporated additives, the format is AdditiveType-Thickness-Units (e.g. TCNQ-20-nm).
  • For solution-mixed additives, the format is AdditiveType-Concentration-Units (e.g. F4TCNQ-10-pww means 10% w/w F4TCNQ).
• dielectric: The dielectric used to make the FET (e.g. Cytop-M, Cytop-S, PMMA).
  • For details, look inside the Library script.
  • NOTE: The dielectric field is used as an input in the DielectricThicknessCalc function of the Library script. The latter has some preset dielectric thicknesses that can be used to extract the mobility.
  • To set the dielectric thickness manually, open the script to be executed (not the Library script itself), comment out DielectricThicknessCalc function and set the dielectricthickness parameter manually.
• DielectricConcentration: The format is either in a v/v ratio, or in g/L (e.g. 3-1, 50-gl).
  • For details, look inside the Library script.
• sampleNo: The number of the sample (e.g. 1st).
• step: The step of the measurement (see the Step Convention section). Applies to EG-OFETs only.
• stepNo: The step number (e.g. 1, 2, 3...)
• deviceNo: The number of the device, if there are multiple devices on the same sample.
• length: The length of the device (distance between the source-drain electrodes). Usually a sample will contain FETs with different channel lengths.
  • The format is No-Units (e.g. 20-um).
  • The value of the width is a parameter that can be adjusted in the script itself. There is no field in the filename from which to extract this value.
• condition(air/N2_liquid): The condition in which the sample has been stored (for shelf-life stability), or is being measured (for operational stability).
  • For example, up-H2O is used for ultrapure water, ss for saline solution, 1-x-PBS for 1xPBS, NaP for NaP buffer. For details, look inside the Library script.
• timelength: The time that the sample has been stored or measured in the respective condition.
  • The format is No-Units (e.g. 20-days, 50-min, 3-h, or just "initial" for the initial day of measurements).
• MeasurementType: T for a transfer curve, O for an output curve, S for a sample (bias stress) measurement (for a sample measurement type (S), the suffix is: S_Vg_Vd).
  • For details, look inside the Library script.
• MeasNo: The measurement number (e.g. 1, 2, 3...). There could be multiple transfer curves taken at a specific time point, so it is necessary to number them.
• MeasurementMode: C for continuous mode, P for pulsed mode
• IntegrationTime: S for short, M for medium and L for large

Filename formats

OFET (Transfer-Output): batchNo_Architecture_material_concentration(No-units)_solvent_annealing_additive (type-thickness-units)_dielectric_DielectricConcentration_sampleNo_deviceNo_length(No-units)_condition(air/N2_liquid)_timelength_MeasurementType(T-O)_MeasNo_MeasurementMode_IntegrationTime

OFET (shelf-life stability): batchNo_Architecture_material_concentration(No-units)_solvent_annealing_additive (type-thickness-units)_dielectric_DielectricConcentration_sampleNo_deviceNo_length(No-units)_"step"_stepNo_condition(air/N2_liquid)_minutesNo-"min"_MeasurementType(T-O)_MeasNo_MeasurementMode_IntegrationTime

OFET (Cryo): batchNo_Architecture_material_concentration(No-units)_solvent_annealing_additive (type-thickness-units)_dielectric_DielectricConcentration_sampleNo_deviceNo_length(No-units)_condition(air/N2_liquid)_timelength_stepNo_air/vac_Temperature_MeasurementType(T-O)_MeasNo_MeasurementMode_IntegrationTime

OFET (Bias Stress): batchNo_Architecture_material_concentration(No-units)_solvent_annealing_additive (type-thickness-units)_dielectric_DielectricConcentration_sampleNo_deviceNo_length(No-units)_condition(air/N2_liquid)_timelength_BiasStressTypeandNo(PBS1/NBS1)_minutesNo-"min"_MeasurementType(T-O-S)_MeasNo_MeasurementMode_IntegrationTime

• NOTE: For S measurement type (sample) the suffix is: S_Vg_Vd.

EG-OGET (sensing-cycling): batchNo_Architecture_material_concentration(No-units)_solvent_annealing_additive (type-thickness-units)_sampleNo_condition(air/N2_liquid)_timelength_MeasurementType(I-vs-time_plunger,valve-port)

batchNo_Architecture_material_concentration(No-units)_solvent_annealing_additive (type-thickness-units)_sampleNo_"step"_stepNo_condition(air/N2_liquid)_minutesNo-"min"_MeasurementType(T-O)_MeasNo_MeasurementMode_IntegrationTime

EG-OGET (operational stability): batchNo_Architecture_material_concentration(No-units)_solvent_annealing_additive (type-thickness-units)_sampleNo_"step"_stepNo_condition(air/N2_liquid)_timelength_MeasurementType(I-vs-time_plunger,valve-port)

batchNo_Architecture_material_concentration(No-units)_solvent_annealing_additive (type-thickness-units)_sampleNo_"step"_stepNo_condition(air/N2_liquid)_minutesNo-"min"_MeasurementType(T-O)_MeasNo_MeasurementMode_IntegrationTime

NMR: batchNo_sampleNo_Method (NMR/SSNMR)_Architecture (film)_material_concentration(No-units)_solvent_annealing_additive (type-thickness-units)_condition(air/N2_liquid)_timelength_MeasNo_frequencyNo-frequencyUnits

batchNo_sampleNo_Method (NMR/SSNMR)_Architecture (solvent)_solvent_condition(air/N2_liquid)_timelength_MeasNo_frequencyNo-frequencyUnits

The step convention

The step data filename convention is only used on EG-OFET data filenames. This convention aims to keep filenames short while keeping track of the sequence of liquids that have been injected in an EG-OFET. Suppose, for example, that we inject ultrapure water for the first 10 minutes, then saline solution for the next 5 hours, and then finally ultrapure water for the next day. Using the step convention, the data filenames would look like this (if we assume one measurement per minute):

• <transistor parameters>_step_1_up-H2O_1-min_<measurement parameters>
• <transistor parameters>_step_1_up-H2O_2-min_<measurement parameters>
• ...
• <transistor parameters>_step_2_ss_1-min_<measurement parameters>
• <transistor parameters>_step_2_ss_2-min_<measurement parameters>
• ...
• <transistor parameters>_step_3_up-H2O_1-min_<measurement parameters>
• ...

Script parameters

Parameters are variables inside the scripts that need to be set up manually, using the CodeBuilder, before the script is run. These parameters are then used to extract various metrics, or to select the correct graph template. We mentioned earlier that the channel width and the dielectricthickness are parameters.

• If the parameters are set up incorrectly, the script will not run properly, or may miscalculate the performance metrics.

The parameters for each script are the following:

OFET parameters

The different parameters found in the OFET processing scripts are:

• Width (W) [um]: The transistor width.
• Length (L) [um]: The transistor length. This is not usually set manually, as a parameter, but is extracted from the length field of the filename. Usually a sample will contain FETs with different channel lengths.
• Thickness of accumulation layer (d) [nm]: The thickness of the accumulation layer.
• Dielectric constant (er): The dielectric constant. Common values include 2.1 for Cytop, 3.6 for PMMA and 3.9 for SiO2.
• Vacuum permittivity (e0) [F/m]: The dielectric permittivity of vacuum is a constant with a value of 8.854E-12.
• Dielectric thickness [nm]: The thickness of the dielectric. This parameter is not usually set manually. It is calculated using the DielectricThicknessCalc function, using the dielectric field as input.
  • NOTE: To set the dielectric thickness manually, open the script to be executed (not the Library script itself), comment out DielectricThicknessCalc function and set the dielectricthickness variable manually.
• Dielectric capacitance (Ci) [F/m²]: The capacitance per unit area of the dielectric. This is calculated by the dielectric thickness and the dielectric constant, using the formula Ci=e0*er/(dielectricthickness*10^(-9).
  • NOTE: This is not completely correct. In reality, there is metal penetration inside the dielectric during the gate evaporation. Hence, we should not take into account the entire dielectric thickness into account when calculating the dielectric capacitance. The correct way to extract the dielectric capacitance is to measure it with an impedance analyzer by short-circuiting the source and drain. Typical values for dielectrics are 3.2 nF/cm² for Cytop and 5.2 nF/cm² for PMMA. From that capacitance, we can extract the effective dielectric thickness, compare it with the measured dielectric thickness and estimate the extent of metal penetration into the dielectric.

Mobility correction (power law fit) parameters

There is a publication that demonstrates how to extract the contact and channel resistance as a function of the gate voltage from the transfer curves, in the linear and saturation regime. The process involves fitting a exponential function to the mobility curve. The fit is performed using the PowerLawFit function that can be called from the Library script.

• To disable this fit, open the script to be executed (not the Library script itself), and comment out the line calling the PowerLawFit function.

The parameters of the PowerLawFit function are:

• minRangeLengthPLF [V]: The minimum voltage range over which the linear fit will be applied. The fit starts at least minRangeLengthPLF volts after the Vgmax point. This number is usually 20.
• errorwindowPLF: The maximum Root Mean Square Error allowed for the fit. If the error is larger than this value then the voltage range in which the fit is performed increases by a single row. Hence, this error defines the "window" for performing the power law fit. The default value is usually 0.001.

Rolling Regression (Vt fit) parameters

The RollingRegression function is used to to calculate the threshold voltage (Vt). It performs a linear fit on part of the drain current (Id) curve, or the √Id curve, and finds the intercept of the fit with the gate voltage (x-axis). This intercept is Vt.

The question is how to determine the voltage range on which to perform the linear fit. One option would be to choose two fixed limits on the voltage axis (e.g. a 20 Volt range) and perform the linear fit in those. If the fit is not good, we can manually change the fit limits and try again. Instead of doing this, the RollingRegression function tries to find the maximum voltage range it can perform a linear fit on before the slope of the linear fit surpasses a pre-determined value that is set in the slopewindow parameter.

• In our FET measurements, the transfer curves are usually scanned with a forward and reverse sweep. Hence, in a typical transfer curve data file, Vgmax = Vg(maxrows/2) where maxrows/2 is the middle row, while the minimum voltages would be at the first and last rows (row 0 and maxrows). The script performs the linear fit in the reverse sweep (i.e. after Vg has reached Vgmax and is reducing). The linear fit is performed at a certain gate voltage range. This range has a left limit and a right limit.
• The function initially sets a minimum voltage range over which the linear fit will be performed. This is the minRangeLength parameter. Thus, the left voltage limit is set at Vgmax, and remains constant. The right voltage limit is set at Vgmax+minRangeLength, and moves to lower voltages (i.e., to the right along the x-axis, or to higher row numbers) with each iteration of the loop. Sometimes an offet is used (see The offset parameters), in which case the left and right voltage limits become Vgmax+offset and Vgmax+minRangeLength+offset respectively. A linear fit is performed at that range, and the value of the slope is stored inside the variable firstfit, since it is the first linear fit performed.
• The iteratively increasing row index i determines the right voltage limit for the linear fit. With each iteration of the loop, the row number i increases by 1, moving to higher row numbers. The right voltage limit is at a gate voltage Vg(i), and moves from Vgmax+minRangeLength+offset to lower voltages (i.e., to the right along the x-axis). At every iteration, a new linear fit is performed in the new voltage range. The percentage difference between the new slope and firstfit is then calculated, and compared against slopewindow. If it is smaller than slopewindow the loop continues into a new iteration, with the right voltage limit moving further away, and a new linear fit being made. Once the percentage difference surpasses slopewindow, the Rolling Regression function stops and we know the voltage range over which to perform the linear fit. Moving the right voltage limit to lower voltages constitutes the rolling window.

So far two parameters have been introduced:

• minRangeLength [V]: The minimum gate voltage range (not row index range!) over which the linear fit will be applied. The more curvy the Id/SQRT(Id) curve, the smaller minRangeLength has to be, in order to be able to fit linearly. Typical values are between 5 and 20, with the default values being 5 for the Linear and 10 for the Saturation regime.

• slopewindow [%]: The limit of the slope of the linear fit (calculated as a percentage relatively to the slope of the first linear fit). Beyond this limit the Rolling Regression function stops and we know the voltage range over which to perform the linear fit. The default values are 1.2 for the Linear and 3 for the Saturation regime.

The offset parameters

We mentioned earlier that sometimes an offet is used, in which case the left and right voltage limits become Vgmax+offset and Vgmax+minRangeLength+offset respectively. This is because there are cases cases when the Rolling Regression function can fail. One such case is when Idmax and Vgmax do not coincide and another is when gm,max (the slope of the Id/SQRT(Id) curve) and Vgmax do not coincide. Two separate offsets, offset1 and offset2 are used to shift the window to lower voltages (i.e., to the right along the x-axis) in each of these two cases.

The RollingRegression function checks and applies both offsets, first offset1 and then offset2. The offsets are summed into a new variable (offset = offset1 + offset2) and the voltage limits for the linear fit are shifted.

The offset-related parameters are:

• autooffset: Setting it to 1 will enable the automatic offset calculation. Setting it to 0 will disable it.
• offset: Manual setting of the offset value, in case autooffset is set to 0. Common offset values include 20 for IDTBT and 0 for N2200 OFETs. The default value is 10. If autooffset is set to 1 this parameter is meaningless, as the offset will be automatically determined.

Offset 1: When Idmax and Vgmax do not coincide

There are cases cases when taking the left integration limit to be Vgmax will cause the Rolling Regression to fail. One such case is when Idmax and Vgmax do not coincide. This is presented in the following Figure:

In this case, Idmax occurs at a different voltage: Vg(Idmax). After Vg(Idmax), the slope of the dId/dV curve turns positive and the resulting linear fit rises to infinity.

To correct for this, the RollingRegression function checks if Idmax and Vgmax coincide. If not, the left voltage limit for the linear fit is shifted from Vgmax to Vgmax+offset1, where offset1 is the voltage difference between Vgmax and Vg(Idmax). The left voltage limit will then start from Vg(Idmax). Hence, offset1 ensures that the linear fit is applied at the voltage range around Idmax. This is presented in the following Figure:

Offset 2: When gm,max and Vgmax do not coincide

Another case when the Rolling Regression can fail is when gm,max and Vgmax do not coincide. This is presented in the following Figures:

In this case, gm,max occurs at a different voltage: Vg(gm,max). The RollingRegression function will start at Vgmax (60 Volts), perform the first linear fit over a voltage range of minRangeLength Volts and then keep iterating until the slope diverges. The divergence happens roughly ~15 Volts away from Vgmax, at 45 Volts. However, this linear fit obviously underestimates the threshold voltage Vt. This is because beyond the 45 Volts the slope (i.e. the transconductance, gm) becomes even larger. The maximum value of the slope (and of the transconductance) occurs at roughly 35 Volts, and this is where the linear fit should have taken place.

To correct for this, the RollingRegression function checks if gm,max and Vgmax coincide. If not, the left voltage limit for the linear fit is shifted from Vgmax to Vgmax+offset2, where offset2 is the voltage difference between Vgmax and Vg(gm,max). The left voltage limit will then start from Vg(gm,max). Hence, offset2 ensures that the linear fit is applied at the voltage range around gm,max. This is presented in the following Figure:

Reliability factor

The reliability factor is calculated as described in the relevant publication.

• A point of uncertainty exists with respect to the denominators of formulas (B1) and (B2) of the publication, which are essentially the transconductance values. The transconductances do not have a single value - they depend on the gate voltage. Hence, it is unclear which value of the transconductance should be used for the calculation of the reliability factor. We could use the maximum transconductance (g_{m, max}), or the transconductance at the maximum gate voltage (g_{m, VGmax}).
• The scripts have been coded to use the maximum transconductance (g_{m, max}) value (which may or may not be at the maximum gate voltage), thus calculating a worst case scenario for the reliability factor.

EG-OFET parameters

• The parameters in EG-OFET scripts are very few and have to do with the StabilityMetrics function that is inside the Library script. This function is called by the EG-OFET scripts and calculates the onset of the steady state Tss when given the ON current evolution over time. The ON current evolution over time, extracted from consecutive transfer curves, is the typical operational stability measurement.
• As shown in the relevant publication, an IDTBT EG-OFET's operational stability profile can be split into two regimes: an initial "regime I", where the ON current of a freshly fabricated device initially overshoots to a high value, then rapidly decreases within the first few measurements, and eventually reaches a steady state at the end of the first overnight experiment, followed by a much slower degradation "regime II", where the ON current can remain stable for the duration of a 900 min overnight experiment, with the baseline decreasing slowly from day to day (i.e., between overnight experiments).

Regime I (left) and regime II (right) are shown in the following Figure:

We need to calculate the onset of the steady state in the ON current curves, and the calculation has to make sense in both regimes. The first method is to calculate the three point derivative of the curves, and restrict it from remaining below a certain limit. That limit is the Tsswindow parameter. The results are shown in the following Figure:

The steady state calculation is accurate for regime II but not for regime I. The three point derivative does not work properly in regime I, as it may have some flat regions.

The second method is to perform a linear fit across the entire time curve, and restrict the slope from remaining below the Tsswindow limit. The results are shown in the following Figure:

The steady state calculation is accurate for regime I but not for regime II. This method does not work properly in the case of a very flat curve, as the large, flat sections will dominate, and allow for the linear fit to ignore the transient region.

The third method is to perform a linear fit in a limited range, and restrict the slope from remaining below the Tsswindow limit. A range of for a range of 200 minutes was chosen. It is like having a 200-min long rod and trying to fit it along the ON current curve until it is flat enough (i.e., until the slopw is below the Tsswindow limit). The fit does not start from t=0 but after the first liquid injection, which takes about 8 minutes. The results are shown in the following Figure:

The steady state calculation is accurate for regime I and regime II. This method is a reasonable compromise. Hence, the onset of the steady state Tss was defined as the time for which the slope of the ON current (drift) remains below a 10^-9 A/min for 200 minutes. The different parameters found in the EG-OFET processing scripts are:

• Tsswindow [A/min]: The maximum value of the slope allowed for the linear fit, in order to extract the onset of the steady state. Typical value is 1E-9.
• minRangeLengthTss [min]: The minimum range of minutes over which the linear fit will be applied. Typical value is 200.
• Twaterinjected [min]: The time in which water has already been injected in the EG-OFET. Typical value is 8. This is the left limit of the linear fit.

Once the onset of the steady state (Tss) is extracted, the following metrics are calculated:

• Idon,SS,mean: Mean ON current at steady state
• Idon,SS,SD: Standard deviation of the ON current at the steady state
• Idon,SS,Range: ON current range (Max Idon)-(Min Idon) at the steady state
• dIdon/dt: Derivative of the ON current at the steady state