Measurement Controller for Electronic Materials

The goal of Lake Shore is “Advancing Science”. In 2018, the company celebrated 50 years since its inception, and its equipment has become an essential aspect of numerous scientific advancements and discoveries during this time.

Specifically, semiconductor researchers and physicists across the globe have been helped by their precision measurement and characterization solutions, enabling them to develop and discover new magnetic and electronic materials. These new materials may enable the technologies of tomorrow.

Lake Shore solutions has enabled research in the following areas: transparent conducting oxides, organic electronics, solar cells, spintronics, dilute magnetic semiconductors, superconductors, and carbon nanotubes.

Delivering Higher Levels of Precision, Speed and Convenience to Researchers in Electronic Materials

The latest addition to Lake Shore’s MeasureReady instruments is the M91 controller. In a typical Hall measurement setup, three or more instruments and a great deal of software are required. The M91 is a single half-rack size instrument which replaces these instruments and software. Consequently, it is a significantly more convenient and compact way of updating an existing Hall measurement system or building a new one.

The M91 is more than just an all-in-one solution, as it features Lake Shore’s new, patented FastHall technology. The time taken to complete a sequence of Hall voltage measurements is reduced by as many as 100 times by this technology. This is particularly the case for certain modern semiconductor materials, whose low mobility or high resistance makes them more difficult to measure.

Challenging material samples, which may have previously been impossible to analyze, can now be analyzed in a matter of minutes.

The amount of time during which external factors, like temperature shifts, can inject unwanted offsets into the data is reduced by the shorter measurement window. This makes results obtained using FastHall more accurate.

Benefits and Features

The core benefits and features of the M91 FastHall controller are:

  • It is more convenient and straightforward to use
    • Measurement setup is automatically optimized
    • Measurement steps are automatically executed
    • Complete Hall analysis is provided, delivering ‘answers’ instead of just output
    • Traditional DC Hall and FastHall modes are both supported
    • Can be easily operated and integrated with existing lab systems
  • Superior measurements are made more quickly
    • When the FastHall mode is used, there is no need to reverse the magnetic field
    • Challenging materials can be measured as much as 100 times faster
    • As thermal drift errors are minimized, accuracy is improved
    • Manual “trial-and-error" steps are eliminated by the automated optimization of measurement range and excitation. This guarantees measurements are always made under conditions which are optimal for the sample
  • Cutting-edge Hall measurement abilities can be added to any lab in a cost-effective way

Comparing the FastHall Approach to the Other Approaches

For semiconductor development and research, the Hall effect measurement is of vital importance. It is used widely in order to ascertain a material or device’s essential parameters, such as carrier type, carrier mobility, carrier concentration, and resistivity.

In general, a voltmeter or current source, together with a magnetic field source such as a superconducting magnet, a permanent magnet, or an electromagnet, are used to accomplish Hall measurements.

A sequence of measurement steps is required for the Hall measurement protocol – initially in order to assess the integrity of the electrical contacts to the sample, and afterwards to measure the resistivity of the sample. Following this, a magnetic field is applied to the sample orthogonally and a series of measurements are taken of the Hall voltage induced across the sample.

In traditional DC field Hall measurements, the sample’s Hall voltage must first be measured using a field applied in one direction. After this, another measurement is taken with an identical field magnitude in the opposite direction.

Historically, separate voltmeters and current sources needed to be assembled for this process, and the switching of instruments was required. This entire process would also need to be coordinated via external PC software, which also needs to collect the measurement data and carry out a number of post-measurement calculations in order to derive the desired material parameters.

In order to get up and running swiftly, certain researchers elect to purchase packaged Hall measurement systems (HMS) from a number of suppliers, including Lake Shore. Others decide to assemble their own system using individual instruments they have acquired, either to save on costs or because they require something more specialized. This includes writing their own software.

Even though the MeasureReadyTM M91 FastHallTM measurement controller is not a packaged HMS, all that is required in order to complete the system is a magnet and a way of holding and connecting your sample. The M91 constitutes a manner of upgrading an existing system or building a new one which is extremely convenient, cost-effective, and rapid.

All of the required HMS instrumentation is also combined in a single, half-rack package in the M91 – including measure, source, and switch functions. All of the firmware required for the optimization and execution of the whole Hall measurement process, gathering the data, and calculating the final mobility and Hall parameters, is included in the instrument.

It is the only instrument on the market which does not require any manual setup and which directly outputs Hall measurement results without the use of PC software for the calculations. Lake Shore’s new FastHall measurement mode is also included in the M91, as well as a mode which supports the undertaking of traditional DC field Hall measurements.

A few years ago, Dr. Jeff Lindemuth invented FastHall. He is an expert in applying Hall effect measurements in order to study new semiconductors, who supports current customers using Lake Shore’s packaged 8400 series HMS.

Dr. Lindemuth realized that although this system was one of very few which were able to measure high resistance and low mobility materials with the use of its unique AC field mode, the measurements produced had extremely small signals and often necessitated long measurement times and a great number of samples.

Dr. Lindemuth’s extensive experience in small signal measurement methods enabled him to create the FastHall method, which is applicable to any samples in a van der Pauw (square, 4 contact) configuration. This is an outstanding breakthrough in semiconductor research.

The M91 FastHall™ Measurement Controller Eliminates the Need to Switch the Polarity of the Applied Magnetic Field During Measurement

The type of magnet used determines the time taken to reverse a field. Electromagnets are limited by coil inductance, superconducting magnets need a great deal of time to transition, and permanent magnets need a physical reorientation of the magnet or sample.

There is no need to switch the field direction in FastHall mode, which gets rid of some unproductive time. This enables users to obtain results much more rapidly, as they can do more science in less time.

Researchers who measure low mobility materials like organic semiconductors, thermoelectrics, and photovoltaics are the particular beneficiaries of this. Previously, only AC field methods were viable options for the measurement of these materials (the magnetic field is being varied continuously during the measurement process in AC field methods). It takes minutes to get equal or improved results with FastHall, where previously it would have taken hours.

This also means that all magnet types are suitable for the FastHall method – superconducting, electromagnet, or permanent. As mentioned previously, while high-field superconducting magnets are pivotal to certain types of Hall analysis, they can take a great deal of time change from positive to negative fields.

It becomes a great deal more efficient to use high-field magnets with FastHall. The speed benefits compound if Hall measurements are needed at a number of field settings – particularly when undertaking quantitative mobility spectrum analysis of devices or materials with numerous carrier types.

Applications which will Benefit from the M91 FastHall Measurement Controller

Materials characterization platform OEMs, semiconductor device developers, and semiconductor material researchers all over the world will want to think about the M91 if they want to upgrade an existing HMS or build a new one.

The instrument can be integrated with other equipment easily and, courtesy of its FastHall ability, it offers superior Hall measurement results over a wider variety of samples than previous solutions.

Extremely low noise circuitry is combined with AC lock-in measurement methods in the M91, enabling the measurement of even extremely small Hall voltages from particularly challenging materials. For instance, materials with very high resistance (up to 200 Gohm or over 10 Mohm) or with extremely low mobility (1 cm/Vs and under, down to 10 cm2/Vs) can be measured.

A copy of the new MeasureLINK-MCS software is included by Lake Shore with each M91. This HMS measurement sequences to be customized by the M91, and it stores and displays the M91’s results. Integration with other third-party lab software and instruments is also facilitated by this software.

As a result of Lake Shore’s extended history working in magnetics and cryogenics, MeasureLINK is, unsurprisingly, designed so that it coordinates with variable temperatures and/or variable magnetic field controllers located on common research platforms (like high-field superconducting magnet systems, cryostats, and cryogenic probe stations). This enables completely automated variable temperature or variable field Hall measurements.

The M91 FastHall Measurement Controller and the Future of Lake Shore Cryotronics

The new M91 instrument from Lake Shore is the result of 20 years of experience in the development of packaged Hall measurement systems (HMS). At present, the company is one of the leading suppliers of solutions for researchers who require Hall effect analysis of early stage devices and materials of a high quality.

For customers who decide to build their own Hall systems, the M91 instrument is affordable. Significant advantages in terms of measurement performance and productivity are offered by the M91, courtesy of the inclusion of FastHall technology. This is particularly useful for researchers who are developing the future generation of advanced semiconductors.

The M91 controller is the newest addition to the MeasureReady series of line measurement instruments, developed by Lake Shore specifically in order to support material characterization applications. More about this will be revealed later in the year.

This information has been sourced, reviewed and adapted from materials provided by Lake Shore Cryotronics Inc.

For more information on this source, please visit Lake Shore Cryotronics Inc.

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