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https://github.com/ssomnath/cantilever_temperature_control

Software for controlling the temperature of a self-heating AFM cantilever
https://github.com/ssomnath/cantilever_temperature_control

afm atomic-force-microscopy characterization igor-pro imaging lithography scanning-probe-microscopy spm temperature-control thermal

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Software for controlling the temperature of a self-heating AFM cantilever

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README 

          
Heated Cantilever Suite

========================

**Suhas Somnath**



University of Illinois Urbana-Champaign



Last Updated: 3/01/2012



.. contents::



Introduction

-------------



This software suite provides the capability to perform experiments such

as thermal nanolithography and thermal topography imaging using heated

micro-cantilevers via the hardware and software of Asylum Research AFMs.

This software suite controls cantilever temperature in closed loop

feedback using the AFM controller’s electronics to improve lithography

and imaging performance of heated cantilevers.



Journal papers using this software

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

1. Somnath, Suhas, Elise A. Corbin, and William P. King. "Improved nanotopography sensing via temperature control of a heated atomic force microscope cantilever." IEEE Sensors Journal 11, no. 11 (2011): 2664-2670.

2. Kim, Hoe Joon, Nicolaie Moldovan, Jonathan R. Felts, Suhas Somnath, Zhenting Dai, Tevis DB Jacobs, Robert W. Carpick, John A. Carlisle, and William P. King. "Ultrananocrystalline diamond tip integrated onto a heated atomic force microscope cantilever." Nanotechnology 23, no. 49 (2012): 495302.

3. Liu, Joseph O., Suhas Somnath, and William P. King. "Heated atomic force microscope cantilever with high resistivity for improved temperature sensitivity." Sensors and Actuators A: Physical 201 (2013): 141-147.

4. Somnath, Suhas, and William P. King. "An investigation of heat transfer between a microcantilever and a substrate for improved thermal topography imaging." Nanotechnology 25, no. 36 (2014): 365501.

5. Somnath, Suhas, Joseph O. Liu, Mete Bakir, Craig B. Prater, and William P. King. "Multifunctional atomic force microscope cantilevers with Lorentz force actuation and self-heating capability." Nanotechnology 25, no. 39 (2014): 395501.



Disclaimer

~~~~~~~~~~~



This code is foreign to the existing AFM software. I have worked around

many issues painstakingly to ensure that this code works as smoothly as

possible. In the same manner, care has been taken to ensure that the

normal AFM operation is not thwarted in any way. Sometimes, when this

package is started up but not used actively, certain native operations

of the AFM software tend to take back certain resources that were

allocated for this code. This may manifest in the form of malfunctioning

temperature control meters, stoppage in the PID controlling the

cantilever temperature, etc. None of these should damage the cantilever

in anyway. To resume normal operation of this code when necessary, use

the reinitialize / refresh buttons provided. Typically, clicking on the

start button is sufficient to bring things back to normal. This code has

been tested extensively and its use has so far never resulted in any

damage to the cantilever or the sample but please be careful when using

this code and be mindful of the fact that this code is still foreign to

the native AFM software.



This software was written from 2009 - 2012 and I provide no guarantee / fixes for making it work today.



Requirements

------------



Software

~~~~~~~~~



* Igor Pro 6.1 or later

* Asylum Research software version: MFP3D 090909+xxxx or later



Hardware

~~~~~~~~~



* Asylum Research MFP-3D or Cypher AFM

* Voltage follower circuit breaker - only for AFM Controllers prior to ARC 2 (2011 Jan or before)

* Silicon Self-heating cantilevers from:



   * UIUC - Prof. William P. King or

   * Anasys Instruments - Thermalever AN200 / AN300 probes - sold commercially



Setup

-----



Electrical connections

~~~~~~~~~~~~~~~~~~~~~~~



Please make sure to use the voltage follower box specially constructed

to circumvent the impedance matching problem of older Asylum Research

AFM controllers for this code to work accurately.



|Schematic|



1. Connect the ``Expansion port`` (25 pin serial) on the ``AFM controller`` to

the ``Voltage follower box``



2. Connect V\ :sub:`S` (voltage across R\ :sub:`S`) to the ``in0`` labeled

on the voltage follower box



3. Connect V\ :sub:`T` to the in1 labeled on the voltage follower box

and to ``BNCout0`` on the AFM controller. You can use a ``BNC T-split`` for

this.



Software Installation

~~~~~~~~~~~~~~~~~~~~~

1. Copy the ``TemperatureControl.ipf`` file into the ``UserIncludes`` folder so that this procedure file is compiled after

   the AFM software.

2. Copy the hacks present in each Asylum source code file in the ``hooks`` folder to the corresponding file used by your AFM.



   * I have used comments with my name to delineate the start and ends of each hack

   * Search for ``Suhas`` to find each of the modifications

   * Modify your file accordingly.

3. Accessing the Heated Cantilever Suite: In the top ``menu bar`` of the AFM

   software: ``UIUC`` >> ``Heated Cantilever Suite`` >>



|image1|



Cantilever Electrical Characterization

---------------------------------------



|image2|



Introduction

~~~~~~~~~~~~~



-  This package is accessed by clicking on ``UIUC`` >> ``Heated Cantilever Suite`` >> ``I-V Characterization``.



-  This package lets you electrically characterize the probe by linearly

   ramping the voltage being applied across the heating circuit.



Parameters

~~~~~~~~~~~



-  ``R sense (k Ohm)``: The resistance of the sense resistor in ``kΩ``. You

   can apply at most ``10V`` with this setup so choose your sense resistor

   that will allow you to access the cantilever temperatures you are

   interested in. I advise you to pick sense resistors in the range of ``1``

   to ``5 kΩ``. The value entered here **will persist** throughout the AFM

   software.



-  ``V initial (V):`` Initial voltage to be applied across the circuit

   (0V <= ``V initial`` <10V). Lower ranges of voltage (0-1V) are typically

   less reliable. 1V should be just fine.



-  ``V final (V)``: Maximum voltage that will be applied across the

   circuit (0V < ``V final`` <= 10V). I advise you to start with something

   small like ``2V`` and go as high as necessary.



-  ``Delay (sec)``: Time delay in seconds between measurement points.

   Larger the delay, greater the number of points of data being

   averaged. Any time greater than 1 sec will not necessarily improve

   the accuracy of the results greatly. Ensure that the delay is at

   least ``250 msec``.



-  ``V step (V)``: Incremental voltage being applied across the circuit

   between measurement points.



-  ``Show data:`` If this is left checked, a table will pop up with the

   results of the IV characterization.



Running an Experiment

~~~~~~~~~~~~~~~~~~~~~~



-  Once the above parameters are specified, you may click the ‘Start’

   button. If it does nothing on the first click, click it again.



-  In the event that you want to stop the ramp at any time, you can do

   so by clicking the "Stop" button.



-  Four graphs are updated in real time as each measurement point is

   acquired. Due to the nature of Igor Pro, the data may appear in an

   awkward manner because Igor Pro considers (0,0) as a point of

   measurement even if it is a virtual point on the graph. This will

   disappear and the data will look the way it should once the ramp is

   completed.



-  The four graphs display circuit properties against actual bias

   applied across the circuit and are as follows in anti-clockwise

   direction:



   -  Cantilever resistance



   -  Voltage across the cantilever



   -  Power supplied to the cantilever



   -  Current through the cantilever



Cantilever Temperature Control Meter

------------------------------------



|image3|



Introduction

~~~~~~~~~~~~~



-  This panel is initialized automatically when either the ``Thermal Lithography`` or

   ``Thermal Imaging`` windows are accessed.



-  This panel can be accessed by clicking on ``UIUC`` >> ``Heated Cantilever Suite`` >> ``Meter Panel``



-  This panel provides real-time information about the cantilever’s

   resistance, power dissipation, voltage across the circuit, current

   through the circuit, etc.



Parameters

~~~~~~~~~~



-  ``Reinitialize``: This button reinitializes the code necessary to run

   this panel



-  ``Refresh``: This button can be used in the rare event that the data

   in the meter stops refreshing.



-  ``PID Status``: This LED provides the status of the ``PID loop`` that

   maintains the cantilever temperature constant:



   -  Green: PID loop running



   -  Yellow: PID loop Initialized but not running



   -  Red: PID loop disabled.



Thermal Lithography

-------------------



|image4|



Introduction

~~~~~~~~~~~~~



-  This package is accessed by clicking on ``UIUC`` >> ``Heated Cantilever Suite`` >> ``Thermal Lithography``



-  This window allows you to perform thermal lithography with a heated

   cantilever. The lithography lines / patterns drawn either using

   ``Microangelo`` or `SmartLitho `_ can be synchronized if appropriate triggers

   are inserted into Asylum's code. With the trigger code inserted, this

   package is capable of switching the cantilever's temperature from

   warm to hot and vice-versa when performing lithography.



-  Once this package is accessed, the ``Temperature Control Meter`` panel

   starts up as well.



Parameters

~~~~~~~~~~



-  ``R sense (k Ohm):`` The resistance of the sense resistor in kilo

   ohms. See notes on the I-V characterization section for more details.



-  ``R Normal (k Ohm):`` This is the cantilever's resistance setpoint to

   be maintained when NOT performing lithography.



-  ``R Litho (k Ohm):`` This is the cantilever resistance setpoint to be

   maintained when performing lithography.



-  ``Start PID:`` This initializes and starts the PID loop that controls

   the cantilever temperature. Start the PID just before performing

   lithography and then click ``Do Litho`` in the ``Litho Panel`` to perform

   lithography. The cantilever will not be heated unless the PID is

   started. When the PID is started, the square window to the right of

   the Start PID button will turn green indicating that the PID is

   currently maintaining constant cantilever temperature.



-  ``Stop PID:`` Should the experiment go awry for some reason, you can

   use this button to stop the heating. If the experiment proceeds

   normally, the heating will be discontinued once the lithography is

   completed or the lithography is aborted by the user by clicking on

   ``Stop Litho`` in the Litho Panel.



**Note** - Due to limitations of Asylum's hardware & software, the above

mentioned cantilever resistance set-points may not be maintained very

accurately (although the precision is very good). For typical purposes,

the inaccuracy should be acceptable. Use the meter panel to tweak the

set-points until the desired set-point is reached in the meter panel.



Don't set the ``Rcant`` setpoint too close to the room temperature

resistance of the cantilever. This causes the PID control to approach a singularity. In this

case ``0 V`` will be applied to the circuit. This will NOT result in damage to the

cantilever.



Cantilever Temperature Ramp

~~~~~~~~~~~~~~~~~~~~~~~~~~~



-  This package also allows slow ramping of cantilever temperature while

   performing lithography. This feature is disabled by default.



-  The cantilever temperature is ramped only while performing

   lithography and not in between lines. Once the lithography of the

   current line / feature is completed and that of the next line starts,

   the temperature ramp starts from the beginning again.



-  The ramp starts with the specified ``R Litho`` and ramps up to ``R max``.



-  ``Ramp Temperature``: This needs to be checked to enable ramping of

   temperature during lithography



-  ``T step (sec)``: This is the time delay before the cantilever

   temperature is incremented



-  ``R max (k Ohm)``: This is the maximum cantilever electrical

   resistance up to which the cantilever temperature will be ramped and

   henceforth held constant till the lithography of the current feature

   ends.



Thermal Topography Imaging

---------------------------



|image5|



Introduction

~~~~~~~~~~~~



-  This package is accessed by clicking on ``UIUC`` >> ``Heated Cantilever Suite`` >> ``Thermal Imaging``



-  This window allows you to perform thermal topography imaging with a

   heated cantilever.



-  Once this package is accessed, the ``Temperature Control Meter`` panel

   starts up as well.



Parameters

~~~~~~~~~~



-  ``R sense (k Ohm):`` The resistance of the sense resistor in kilo

   ohms. See notes on the ``I-V characterization`` section for more details.



-  ``R cant (k Ohm):`` This is the cantilever's resistance setpoint to

   be maintained when performing topography imaging.



-  ``Scan Mode:`` This allows the user to choose the mode of actuation

   of the cantilever when imaging. The lateral channel has been used to

   display the voltage across the cantilever. This imaging window should

   be initialized automatically. Setting the mode of imaging here allows

   the software to set up the imaging windows among other parameters

   accordingly:



   -  ``Thermal Feedback:`` This is a beta testing feature. Please don’t

      use this. Instead, please use the contact mode and tapping modes

      of imaging only.



-  ``Start PID:`` This initializes and starts the PID loop that controls

   the cantilever temperature. Start the PID just before performing

   imaging and then click ``Do Scan`` in the ``Master Panel`` to perform

   topography imaging. The cantilever will not be heated unless the PID

   is started. When the PID is started, the square window to the right

   of the Start PID button will turn green indicating that the PID is

   currently maintaining constant cantilever temperature.



-  ``Stop PID:`` Should the experiment go awry for some reason, you can

   use this button to stop the heating. If the experiment proceeds

   normally, the heating will be discontinued once the imaging is

   completed or the imaging is aborted by the user by clicking on ``Stop Scan`` in the ``Master Panel``.



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