High Level Performance for the SPM Market

Craig Wall, PhD, Director of Marketing, talks to AZoNano about the new awarding winning PanScan Freedom Cryogen-Free LT AFM / STM and the high level performance it offers the SPM market.

Please could you give our readers an introduction to the new PanScan Freedom system?

The recently launched PanScan Freedom brings something entirely new to the field of low temp SPM; the ability to routinely study samples at temperatures near 9 Kelvin without using any liquid cryogens, more specifically liquid helium. Our proprietary interface and noise isolation system allow us to use a closed cycle cryostat to provide probe and sample cooling yielding the benefits of:

• Liquid He-free
• Cryogen cost-free
• Interruption-free
• Atomic resolution 9-400 K
• XY drift as low as 0.2Å/hour
• Z drift as low as 0.2Å/day
• Superb stability for spectroscopy measurements

Traditionally SPM systems utilize liquid helium at a very high cost for the user. How have you developed the PanScan Freedom to reduce these costs?

Competing low temperature ultra high vacuum scanning probe microscopes (UHV SPM) consume liquid helium to reach sample temperatures of 10 Kelvin. The typical researcher using the PanScan Freedom will save $200,000 in liquid helium costs over the lifetime of the instrument (ca. 10 years, based on current liquid helium costs). The PanScan Freedom not only saves in operating costs it frees up precious helium resources for other areas of research where there is no alternative to liquid helium.

In addition to saving on liquid helium, the ease of operation of the PanScan Freedom provides all of the low temperature benefits of reduced atomic motion, surface diffusion, lower noise/higher quality spectroscopy, and studying temperature dependent transitions without any of the problems of using liquid helium. Many scientists are passingly aware of these benefits but the ease of use pain point of UVH/LT is often the biggest barrier. We can now overcome this with the PanScan Freedom.

Cryogen-free SPMs have struggled to match the performance of older SPM designs due to the high vibration and acoustic noise of the helium-free cryostats. How has RHK Technology developed the PanScan Freedom to match this performance?

The PanScan Freedom is based on the (Shuheng) Pan style scanner, which is coupled to a closed-cycle cryostat. RHK has worked closely with Advanced Research Systems to develop a custom closed-cycle cryostat system with a uniquely low level of vibration at the cold finger. PanScan Freedom utilizes an advanced multi-stage vibration isolation system with a highly optimized vibration damping system to eliminate the vibrations from the cryostat.

The entire microscope, including the probe and sample are held at precisely the same temperature. Eliminating thermal gradients reduces drift to an extremely low level, with X,Y drift to as low as 0.2Å/hour and Z drift as low as 0.2Å/day.

The PanScan Freedom has a symmetric design, which automatically helps compensate for thermal drift. Dual thermal shields fully isolate the scan head from the room temperature of the chamber, helping keep the scan head at a low and steady temperature.

RHK recently completed the PanScan Freedom world tour. Could you tell our readers how the tour went and how the PanScan Freedom performed in the different environments?

Even noisy environments do not degrade performance, which was proven running the PanScan Freedom live on the exhibition floor during AVS 2014, APS 2015, DPG 2015, AVS 2015, and APS 2016. Our next stop is IVC-20 in Korea in August 2016.

The PanScan Freedom systems performed flawlessly at each of these venues. Atomic resolution data was routinely demonstrated, independent of environmental noise and crowds of people.

Seeing is believing, most scientists assumed that a cryogen-free SPM could never reach the level of performance of the older generation of previous designs due to the high vibration and acoustic noise of the helium-free cryostats. In addition, showing the real-world performance of the instrument as opposed to a few “hero” image data examples, is a much more powerful demonstration of the PanScan Freedom’s capabilities.

AVS2014

APS2015

DPG2015

AVS2015

APS2016

Who is the PanScan Freedom aimed at?

The Pan Scan Freedom is perfect for researchers that would have never previously considered a cryogenic SPM due to the high cost and complicated operation. The PanScan Freedom’s ease of operation and low cost of ownership will provide a dramatic improvement in all STM, spectroscopy and AFM measurements. Lower noise, more stable tip and sample, and dramatically lower drift to greatly improve productivity.

Have you been able to achieve ultra-low noise atomic structures on a variety of materials?

Visualization of surface structures with atomic scale resolution is the main function of the SPM. The practical realization of ultra low noise atomic structures has been demonstrated by the PanScan Freedom on a variety of materials from crystalline metals, semiconductors, topological insulators, to carbon nanotubes. PanScan Freedom has also demonstrated low-noise, low-drift, atomic resolution scanning tunnelling spectroscopy mapping, all without consuming a drop of liquid helium.

Do you have any case studies that you are particularly proud of?

One of our more interesting cases was a PanScan Freedom system for Rob Moore’s group at SLAC (Stanford Linear Accelerator) which interfaced to an existing MBE system. I believe that this example is best explained with the following quote from Rob Moore.

We have a very challenging environment for an STM and RHK was willing to work with us to ensure that a customized solution would not only couple to our existing system but be able to perform as advertised. While other vendor’s visited our lab and conducted vibration measurements with accelerometers, RHK went so far as to bring an actual scanning stage and electronics to our lab to evaluate how well it would perform in our lab. While your scientist indicated it was the worst environment he had encountered, he also remarked that the scanner had performed better than expected.  Such attention to details and extensive evaluation of the situation is what makes RHK stand above other vendors. It is clear that your scanner is the only one that will provide world-class data in our environment and you were willing to prove it prior to purchase.

Due to the sensitivity of ARPES to magnetic fields we have cryopumps on our vacuum system and thus we know how much vibration they create.  Knowing that RHK is confident enough in their scanner to provide a cryocooled manipulator gives us confidence that the noise and vibrations on the synchrotron experimental floor will not be an issue for your instrument. In addition, liquid helium is a scarce resource that is becoming increasingly expensive.  Additionally, several projects in our lab were impacted by the recent helium shortages. Having a cryogen free cooling stage will not only save us tens of thousands of dollars annually, but will ensure continuous operation without relying on such a scarce resource. Cryogen free systems are becoming a necessity in low temperature research and designing a scanning probe microscopy that has superior performance while utilizing such a system shows how RHK is leading the industry in their field and how they are continually pushing the envelope.

Rob Moore

Does the PanScan Freedom offer both STM and AFM capabilities?

The PanScan Freedom is available with STM only or with both STM and AFM capabilities. AFM-qPlus and STM probes are switchable in vacuum. qPlus(registered trademark of Professor Franz Gießibl) sensors include a conductive tip for combined AFM and STM scanning techniques. Both of these complimentary proximal probe techniques provide atomic resolution. The unique value of AFM is its applicability to a broader range of materials, especially insulators. By utilizing probe holders with the same mounting base, you can easily load both STM and AFM-qPlus probes into the tip storage positions and switch between them in situ.

What are the next steps in the development of the PanScan Freedom?

One of the key items on our roadmap is the addition of a magnet, which can supply a 2-6 Tesla magnetic field at the sample. There has been strong interest and many recent discoveries in low temperature measurements on multiferoics. We have orders for PanScan Freedom prototypes that incorporate a magnet. The first prototype system of the PanScan Freedom Tesla is due to be installed next month (August 2016).

Where can our readers learn more?

www.rhk-tech.com or contact our sales team at [email protected]

About Craig Wall

Craig Wall joined RHK Technology as Director of Marketing in 2014, for RHK’s line of scanning probe microscopes and control electronics.

Dr. Craig Wall brings over 25 years of scanning probe microscopy, product marketing, and product management experience.

Dr. Wall has also held positions with Goodyear, Molecular Imaging, Agilent Technologies, and NT-MDT Development.

Dr. Wall holds a BS in Chemistry from the University of Texas, Austin and a Ph.D. in Chemistry from the University of North Carolina, Chapel Hill.