Advancing Science with MeasureReady™ M91 FastHall™ Measurement Controller for Electronic Materials

Interview conducted by Mychealla RiceApr 26 2019

In this AZoNano interview, Rob Ellis, VP of Strategic Planning for Lake Shore Cryotronics, talks about their new product, the MeasureReady™ M91 FastHall™ measurement controller—a revolutionary, all-in-one instrument that delivers significantly higher levels of precision, speed, and convenience to researchers involved in the study of electronic materials.

Can you tell us about Lake Shore Cryotronics and the work you do?

Lake Shore’s mission is “Advancing Science.” The company celebrated its 50^th anniversary in 2018 and Lake Shore equipment has been a key part of many scientific discoveries and advancements throughout those years.  In particular, our precision measurement and characterization solutions help physicists and semiconductor researchers in labs around the world discover and develop new electronic and magnetic materials, many of which will enable tomorrow’s technologies.  Some examples of research enabled by Lake Shore solutions include: carbon nanotubes, superconductors, dilute magnetic semiconductors, spintronics, solar cells, organic electronics, and transparent conducting oxides.

The M91 FastHall™ measurement controller is a new approach to Hall measurement. How can it deliver higher levels of precision, speed, and convenience to researchers in electronic materials research?

The M91 controller is the newest addition to Lake Shore’s MeasureReady™ instrument family. It is a single half-rack size instrument that replaces three or more instruments and a lot of software in a typical Hall measurement setup. It is a far more compact and convenient way to build a new Hall measurement system or update an existing one.

In addition to being an all-in-one solution, the M91 features Lake Shore’s patented new FastHall™ technology which reduces the time required to complete a sequence of Hall voltage measurements by a factor of up to 100x, especially with some modern semiconductor materials that are more difficult to measure due to high resistance or low mobility.

Analysis of a challenging material sample that previously may not have been possible can now be done in a few minutes.

A shorter measurement window also reduces the amount of time that external factors such as temperature shifts can inject unwanted offsets into the data. So, results using FastHall are more accurate.  

What are the main features and benefits?

The main features and benefits of the the M91 FastHall controller include:

• Simpler and more convenient to use:
  • Automatically optimizes measurement setup
  • Automatically executes measurement steps
  • Provides complete Hall analysis – outputs “answers” not just data
  • Supports both FastHall and traditional DC Hall modes
  • Easy to use and integrate with existing lab systems
• Makes better measurements, faster:
  • No need to reverse the magnetic field when using FastHall mode
  • Measures challenging materials up to 100x faster
  • Improves accuracy by minimizing thermal drift errors
  • Automated optimization of excitation and measurement range eliminates manual “trial-and-error” steps and assures that measurements are always made under optimal conditions for the sample
• Cost effective way to add state-of-the-art Hall measurement capability to any lab

How does it compare to traditional Hall effect measurement system on the market? How does the FastHall approach compare to other approaches?

The Hall effect measurement is an important step in semiconductor research and development. It's widely used to determine key parameters of a material or device such as resistivity, carrier mobility, carrier type, and carrier concentration.

Hall measurements are generally accomplished using a current source and voltmeter, as well as a source of magnetic field such as a permanent magnet, electromagnet, or superconducting magnet. The Hall measurement protocol requires a sequence of measurement steps – first to check the integrity of the electrical contacts to the sample, then to measure the sample’s resistivity. A magnetic field is then applied orthogonally to the sample and a series of measurements of the Hall voltage induced across the sample are taken.

Traditional DC field Hall measurement requires that the sample’s Hall voltage first be measured with a field applied in one direction, followed by another measurement with the same field magnitude in the opposite direction.

In the past, this process required assembling separate current sources, voltmeters, and switching instruments, while coordinating the entire process via external PC software. That software must also collect the measurement data and perform a series of post-measurement calculations to derive the material parameters desired.

Some researchers choose to buy packaged Hall measurement systems (HMS) from various suppliers, including Lake Shore, as a way to get up and running quickly. Others choose to acquire individual instruments and assemble their own system – including writing software — perhaps for cost savings or because they want something more specialized.

The MeasureReady™ M91 FastHall™ measurement controller is not a packaged HMS, but all you need to complete the system is a magnet and a way to hold and connect your sample. The M91 is a very convenient, rapid, and cost-effective way to build a new system or upgrade an existing one.

The M91 also combines all of the necessary HMS instrumentation — source, measure, and switch functions — in a single, half-rack package. The instrument includes all the firmware needed to optimize and execute the entire Hall measurement process, collect the data, and calculate the final Hall and mobility parameters. It’s the only instrument on the market that needs no manual setup and outputs Hall measurement results directly without using PC software for the calculations.  

The M91 also includes Lake Shore’s new FastHall measurement mode in addition to a mode that supports making traditional DC field Hall measurements.

FastHall was invented a couple of years ago by Lake Shore’s Dr. Jeff Lindemuth. Jeff is an expert in the application of Hall effect measurement to the study of new semiconductors and supports customers who presently use Lake Shore’s packaged 8400 Series HMS.  Jeff recognized that while that system was one of the few capable of measuring low mobility and high resistance materials using its unique AC field mode, those measurements have very small signals and often require large number of samples and long measurement times.  Jeff’s vast experience in small signal measurement techniques led him to develop the FastHall method, which can be applied to any sample in a van der Pauw (square, 4 contact) configuration, and is nothing short of a breakthrough for semiconductor research.  

The M91 FastHall™ measurement controller eliminates the need to switch the polarity of the applied magnetic field during measurement? What benefit will this have?

The time taken to reverse a field depends on the magnet type: permanent magnets require a physical reorientation of the sample or magnet, electromagnets are limited by coil inductance, and superconducting magnets require a significant time to transition.

In FastHall mode, not having to switch the field direction eliminates some unproductive time and means that users get their results faster – basically, they can do more science in less time.

This is especially beneficial to researchers measuring low mobility materials such as photovoltaics, thermoelectrics, and organic semiconductors where previously only AC field techniques were viable (AC field methods are continuously varying the magnetic field during the measurement process). With FastHall, researchers get equivalent or better results in minutes vs. hours.

It also means that the FastHall method can be used with any magnet type — permanent, electromagnet, or superconducting. High-field superconducting magnets are crucial to some types of Hall analysis but, as noted, can take a very long time to switch from positive to negative field. With FastHall, it becomes far more efficient to use high-field magnets. If Hall measurements are desired at multiple field settings, especially when conducting quantitative mobility spectrum analysis of materials or devices with multiple carrier types, then the speed benefits compound.

The MeasureReady™ M91 FastHall™ measurement controller combines all of the necessary HMS functions into a single instrument, automating and optimizing the measurement process, and directly reporting the desired parameters. What applications will benefit from the M91 FastHall measurement controller? How?

Semiconductor material researchers, semiconductor device developers, and materials characterization platform OEMs across the globe will want to consider the M91 if they are thinking about building a new HMS or upgrading an existing one.  The instrument is simple to integrate with other equipment and, with the FastHall capability, provides better Hall measurement results across a broader range of samples than previous solutions.  

The M91 also employs very low noise circuitry coupled with AC lock-in measurement techniques so that even very small Hall voltages from the most challenging materials can be reliably measured such as with very low mobility materials (1 cm²/Vs and below, down to 10^-3 cm²/Vs) or very high resistance materials (over 10 Mohm, up to 200 Gohm).

With each M91, Lake Shore includes a copy of the new MeasureLINK-MCS software which enables customization of the HMS measurement sequences executed by the M91 and displays and stores the M91's results. The software also facilitates integration with other third-party lab instruments and software.

Not surprisingly, due to Lake Shore’s long history in cryogenics and magnetics, MeasureLINK is designed to coordinate with variable temperatures and/or variable magnetic field controllers found on common research platforms — such as cryostats, cryogenic probe stations, and high-field superconducting magnet systems — to enable fully automated variable temperature/variable field Hall measurement.

What does the M91 FastHall measurement controller mean for the future of Lake Shore Cryotronics?

Lake Shore’s new M91 instrument is a culmination of 20 years' experience developing packaged Hall measurement systems (HMS). The company is currently a leading supplier of solutions for researchers needing high quality Hall effect analysis of early stage materials and devices. The M91 instrument is affordable to those customers who choose to build their own Hall systems. With the inclusion of FastHall technology, the M91 provides a significant advantage in productivity and measurement performance to researchers involved in developing the next generation of advanced semiconductors.

In addition, the M91 controller represents the latest addition to Lake Shore’s new MeasureReady line of measurement instruments developed specifically to support material characterization applications. Stay tuned for more on that story later this year!

Where can our readers go to find out more?

Go to www.lakeshore.com and follow the link on the Home page to the MeasureReady Instruments section.

About Rob Ellis

Rob Ellis is VP of Strategic Planning for Lake Shore and is responsible for leading the marketing and product management functions within the company. He received his B.S. in Electrical Engineering from the California Institute of Technology in 1977 and his MBA from The Ohio State University in 1987.

Before joining Lake Shore in 2010 as Director of Strategic Planning, Rob held positions in technical product management, marketing, and business development with a variety of technology companies, including Director of Marketing with Pinnacle Data Systems (now part of Avnet) and Strategic Business Development Manager with Eaton Cutler‐Hammer (now part of Eaton Electrical).