All questions concerning our products like the performance of our TeraSpike microprobe or it's integration into your system are listed here.
Basically, most femtosecond pulse oscillator systems with λ < 860 nm are compatible with our microprobes. The TeraSpike microprobe is optimized for femtosecond pulse excitation with a central wavelength around 800nm and a few mW of average optical power at repitition rates around of 80MHz.
To get an assessment about the microprobe compatibility with your specific laser-system, please don't hesitate to contact us.
No, TeraSpike microprobes fill the gap between diffraction limited mm-scale resolution and AFM-based nm-scale resolution systems. Micron-scale resolution is achieved by using large-scale translation stages and (optionally) using optical surface distance monitoring. This helps to keep the system costs comparatively low and enables measurements over large-scale areas.
You find some exemplary data in our brochure (2MB PDF). The time-domain signal form received by the probe is also depending on the applied emitter and excitation pulse duration which may differ from system to system.
I already own a free-space THz TDS system. Is it possible to integrate the TeraSpike microprobe and perform near-field measurements?
The integration of TeraSpike microprobes into an existing TDS system is usually quite simple. Especially if the system is including a photoconductive detector: In this case most required components should be already available.
With our Sub-System components the effort for system integration is further minimized. These modules contain the required fixtures, mirrors, stages, microprobe mount and focusing lens.
We would like to measure samples which are opaque for THz radiation. Is it possible to measure in reflection?
THz near-field measurements in reflection mode are principally possible using the TeraSpike microprobe, however there are some limitations in comparison to transmission mode. For example, THz excitation under normal incidence is not possible with a probe being vertically aligned to the sample surface because of THz excitation beam masking by the probe. The required oblique THz excitation beam (or probe) alignment is making signal interpretation more demanding in comparison to transmission mode configuration.
The performance of the microprobe can be strongly impaired by a cable or current amplifier of low quality. We recommend the use of our proven accessory components and sub-systems.
If you are not sure weather your equipment is sufficient to operate a TeraSpike microprobe please contact us.
The effective dynamic range depends on your measurement scheme (e.g. ECOPS or Lock-in), the used emitter, integration time and other factors of the setup. With the TeraSpike TD-800-X-HS we are usually working with a signal-to-noise-ration of 30dB in field-amplitude at short lock-in integration times well below 100ms.
We are currently developing a complete standard THz nearfield system. In the mean time we can construct a custom system depending on your specifications. Please contact us and tell us what you need.
Why is the main breadboard mounted vertically in your sub-system D-B2? Is there a particular reason for this rather vertical than horizontal alignment of the laser beam?
This vertical alignment of the subsystem is chosen to allow the horizontal alignment of the sample. This facilitates the sample placement into the setup as gravity does not work against you. Also the integration of translation stages for raster scanning is often simpler with this alignment.
Counting 0.000000000001 times to 1 will take you roundabout a picosecond.
Frequent questions about handling and measurement set-up.
Which orientations of THz excitation beam, sample surface and TeraSpike microprobe do you recommend?
For highest resolution we recommend to align the microprobe cantilever and THz excitation beam in vertical direction to the samples surface. Optical excitation of the TeraSpike is recommended from the non-metalized side of the cantilever as specified in the application notes in our download section.
The distance between the microprobe tip and the device under test should usually be approx. in the range of the targeted resolution.
A manual adjustment of the tip height can be done very easily (using a manual translation stage as integrated in sub-system D-B1 or D-B2). Due to the flexibility of the microprobe cantilever the tip can be brought in slight contact with the sample surface without damaging sample or probe-tip. This process should be visually controlled using a camera with a magnifying objective. This way it is also possible to adjust an eventual sample tilt and to adjust a defined microprobe-to-sample distance.
Another elegant solution is to integrate a separate distance sensor and a 3D-translation stage to achieve a controlled and constant sample/probe-tip distance during scanning.
The probe beam has to stay focused and stable on the photo-switch of the microprobe during the measurements. For probe beam alignment you should use the photocurrent under applied bias voltage as a feedback signal.
How do I make sure that the probe laser beam is staying fixed on the microprobe photo-switch during scanning?
We recommend to move the sample and keep the microprobe position fixed. A continuous re-alignment of the focus is not necessary in this case. For the alignment of the focus on the microprobe the photocurrent at 1V bias voltage can be utilized as an adjustment feedback. A CCD microscope camera is helpful to visually check the spot diameter and position on the microprobe tip.
The recommended microprobe orientation and the range of laser beam excitation angles are given in our application notes (PDF file). The highest photocurrent for a given excitation power is achieved from the cantilever back-side. An optical excitation from the top-side of the cantilever (carrying the electrode structures) is possible as well, but will result in a decreased photo-current.
Even at very short microprobe-to-sample distances a standard optical table with standard vibration isolation is usually sufficient to make undistorted measurements. However, vibration sources should not be placed on the optical table directly if possible. Mechanical choppers are usually uncritical, as long as there is a sufficient distance to the microprobe.
We would like to keep the sample fixed during the measurement. Is it possible to move the microprobe instead?
In principle yes, but the optical excitation beam of course needs to follow the tip (e.g. by using an optical fiber). Unless your sample is extremely large it is usually the most stable and cost efficient solution to move the sample and keep the microprobe in a fixed position.
Measurement services by Protemics GmbH offer an easy access to THz-based high resolution sample analytics. Frequent questions related to this topic are answerd here.
THz analytics (especially THz micro-analytics) is a very new technique and hence the extend of all potential applications is not yet totally clear. Our experts do have a large experience in different kinds of applications and will be pleased to discuss with you your application and the possible benefits of THz microprobing. So please do not hesitate to contact us for a discussion without any obligation.
Of course, all informations regarding the measurement service and the results will be kept strictly confidential unless otherwise explicitly agreed on.
Our customers are free to publish measurement data in accordance to our general terms and conditions.
Service fees are based on the required time effort for the full analysis and reporting. The measurement time depends on sample size, scanning resolution and sample transmission properties. Based on the measurement requirements and sample information you send to us we will prepare the quote for you.
Typically, measurement reports are sent in a 2-3 weeks after the arrival of the sample. In urgent cases please contact us to appoint shorter times.
The transmission of the THz-Signal through a thin layer is related to it's conductivity. This can be described by the Tinkham-formula. Therefore by having a known reference value one can calculate the sheet conductivity from the THz transmission. A detailed description can be found in this publication:
M. Nagel, A. Safiei, S. Sawallich, C. Matheisen, T. M. Pletzer, A. A. Mewe, N. J. C. M. van der Borg, I. Cesar, H. Kurz: „THz microprobe system for contact-free high-resolution sheet resistance imaging," 28th European Photovoltaic Solar Energy Conference and Exhibition, pp. 856-860 (2013) [PDF]
Not generally. We have the possibility to measure 3d-surfaces as long as the height variation does not extend 2mm. Though a crucial point are thickness variations:
If your samples thickness is not constant over the measurment area, this has to be compensated during the measurement. Therefore the time consumption of the measurement increases.
The necessary acquisition time for the correction of thickness variations depends on the range of those thickness variations. As a first estimation one can say, that every 10µm of thickness variation an additional aquisition of the scan area is needed.
Questions concerning shipping, lead time, custom regulations and sales in general are answered in this category.
Our general terms of delivery are FCA - Free Carrier from Otto-Blumenthal-Str. 25, Aachen, Germany.
This means we will do the export declaration at the german customs and the buyer is responsible for shipping, import and possible duty and taxes.
Though, to keep things easy we also offer shipping (prices can be found in the quote).
Our usual maximum lead time is 6 weeks after incoming order. Shorter lead times may be offered depending on the requested product.
Custom solutions have individual lead times, please contact us for more information.
We are also shipping to Asia, though if your are not familiar with import matters please contact us, we will refer you to a local sales partner.
No, they are not. Please contact us if you require assistance.
Yes, we can ship over your personal account. Please drop us a note in your request.