Scanning Tunneling Microscopy

Scanning Tunneling Microscopy

  • Rupali G. Mane added an answer:
    Is it possible to measure the work function of a metal surface with adsorbed gas molecules using STM (scanning tunneling microscopy)?
    We are looking for methods to measure the work function of metal surfaces with polyatomic gas molecules.
    Rupali Mane · Bhabha Atomic Research Centre
    Thanks to Jaun De Miguel
  • Ali Salehizadeh asked a question:
    Are there any available lab positions for collaboration in SEM and TEM?
    I am a Physics Engineering PhD Student at the University of Aveiro, Portugal, and looking for an expert lab for electron microscopy, preferably in Europe or the US, to do SEM or TEM and publish a paper. I should mention that my sample is iron oxide nano particles embedded in silica shells.
  • Rainer Christoph added an answer:
    What is the best vibration isolation solution for AFM?
    Are the isolation tables using nitrogen or compressed air supply the best? What do you think about the active isolation platforms available from Herzan and Accurion that runs simply on electricity?
    Rainer Christoph · Nanotecnia
    Whilst working with Heini Rohrer and Christoph Gerber, I learnt that when a hanging suspension elongates 25cm under the combined weight of AFM & support platform, the system oscillates with a main resonance frequency of aprox. 1 s-1. This can be calculated and measured.
  • Daniil Bratashov added an answer:
    Why do I get these streaks in the background in all my AFM images on Mica substrate?
    Please see this attached image. I am using tapping mode in air. I have tried different probes, but no help.
    Daniil Bratashov · Saratov State University
    It is harmonic generation with period(s) defined by feedback loop delay and usually it is perpendicular to fast scanning axis (if you clear the highest harmonic from image above, you can see slight vertical lines on Fourier spectrum). Beside this generation, the ill-tuned scanning system can catch another sources of noise (50/60 Hz harmonics from electrical noise, around a 1-3 kHz in acoustic noise from ventilation and electrical from inverter and so on). I have seen up to 5 different noise frequencies in very bad tuned scan in my practice. As noise is sampled with regular interval, it frequency can move to the low freqs. region as difference between sampling and noise freqs. (an so it will appear along slow scanning axis).
  • Gopalakrishnan Ramalingam added an answer:
    Is metal contact between the epitaxial graphene sample and the metal sample substrate imperative in order to take STM images?
    I use a UHV growth chamber for High-T graphitization and the SiC substrate is placed on a metal plate (sample holder). I supposed to transfer the sample into the STM chamber connecting to the growth chamber directly after the graphitization. but i couldn't get stable scan condition, therefore no images. I wonder if it is necessary to make metal contact between the sample and the metal plate(the same sample holder used for graphitization)
    Gopalakrishnan Ramalingam · University of Virginia
    You can use Ag paste in UHV. You just need to pump your sample longer in the loadlock before transferring into the chamber so that the volatiles from the paste are outgassed. We generally outgas our samples overnight to avoid destroying the UHV; try not to use more than necessary. We use Ag paste all the time for good contact between graphite and our Mo-sample plate. Good luck!
  • Meysam Nobakht added an answer:
    Can anyone help me to find a comprehensive review papers about applications of synchrotron?
    I want to know what the advantages are of synchrotron radiation for material analysis in comparison with conventional methods? I searched through the internet but I couldn't find anything helpful.
    Meysam Nobakht · University of Isfahan
    thank you dear Timothy Hyde. you help me so much.
  • Sara Ataran added an answer:
    How can I make the thin film top of the surface with STM preparation chamber?
    I used evaporation in preparation chamber, but it was thicker than thin film.
    Sara Ataran · Lund University
    Thank you all for your answers, these are so useful for me.
  • Matúš Dubecký added an answer:
    Does anyone know how Au to Au will be build a schottky contact?
    I have read a artical from Surface Science 600 (2006) 442–447 which describes that STM tip of Au was used to probe a Au island ,between the tip and island will form a Schottky contact when appropriate gold thickness (such as 0.2nm).
  • Lijo Francis added an answer:
    After a hydrogen molecule, do you think we can see a bigger molecule soon or it is the limit?
    Few days ago, it was announced that researchers in China reported the first visualisation of a hydrogen bond using atomic force microscopy (AFM).In May, Felix Fischer and colleagues at the University of California Berkeley in the US used AFM to image molecules before and after a chemical transformation. The remarkable images showed the formation of covalent bonds in a cyclisation reaction. In the latest study to visualise molecules, Xiaohui Qiu and colleagues at the National Centre for Nanoscience and Technology, China, went one step further. They used the same non-contact AFM as Fischer, but instead of looking for covalent bonds they tweaked it to look for weaker interactions. Do you think we had reached the limit of magnification or we can see bigger molecule soon? http://www.rsc.org/chemistryworld/2013/09/first-pictures-hydrogen-bonds-unveiled-afm
    Lijo Francis · King Abdullah University of Science and Technology
    Prof. Walid. yes I meant it. I believe that a lot of things yet to come either in the same phase or in different aspects, and we can not stop at one point.
  • A. Bensouici asked a question:
    What are the parameters to be considered in account to obtain accurate results in I-V measurements using home-made STM?
    STM measurements of semiconducting surfaces.
  • Régis Bisson asked a question:
    Can you suggest a power inverter to protect instruments against overvoltage/power-cut without inducing spurious signal in discriminator/electrometer?
    I am looking for power inverter (220V, 50Hz) suitable for protection of sensitive instruments like STM / EELS / AES / QMS (power consumption ~250W) against overvoltage from power-provider and power cut up to 4-5 hours. It should specifically not induce any spurious signal in measurements from discriminators / electrometers when running on battery during a power cut. I would very much appreciate any advice and feedback on any devices you may have tried.
  • Jeffrey J Weimer added an answer:
    What is the temperature dependence of PZT and the effect on the calibration of AFM?
    The curve which shows "extension deviation of PZT Vs. temperature" is very useful.
    Jeffrey Weimer · University of Alabama in Huntsville
    One remaining note here. The thermal term would be an issue when you have one of two cases. Either, your work is done at a temperature that is significantly different enough from the calibration temperature or your work is done in an environment where the temperature fluctuates dramatically enough over the course of a measurement. In either case, the relative uncertainty in z position of the piezo will be on the order of $\alpha_T\ \Delta T$.
  • Joshua White added an answer:
    How are SDH STM-1 multiplexors synchronized?
    STM-1 synchronization How are SDH STM-1 multiplexors synchronized?
    Joshua White · Clarkson University
    To build on what Yaakov Stein said, the Stratum levels are a standard for NTP (Network Time Protocol - See RFC 1305). A Stratum 0 clock uses GPS for synchronism among network elements. Stratum1 servers / network devices get there information from a stratum 0 system and pass it on over the network, and so on for the various levels. Typical SONET networks use a stratum 0 device at their core and source there clocks from it. STM-1 multiplexers rely on the Stratum 1 that results.
  • Berndt Koslowski added an answer:
    Why do we get negative voltages in barrier height images and how to remove them?
    Barrier height imaging is auxilary to scanning tunneling microscope. The barrier height images are collected from lock-in-amplifier. Observation: some times there is an amplitude dampening (of the applied modulation to the z-piezo) in the signal (observed from an oscilloscope) even before it enters the lock-in-amplifier.
    Berndt Koslowski · Universität Ulm
    Since I(z) is strictly monotonic (non-resonant tunneling, no strange effects) sign reversal of the lock-in signal must be an artifact. There are many sources of such artifacts. The most prominent may be scanning too fast such that the tunneling current undergoes changes (feedback too slow). Another source may be time dependent distortions in the tunneling current. Check your tunneling current signal for unexpected changes/distortions.
  • Jagadish Chandra Mahato asked a question:
    During Current-Voltage measurement, the sample bias and the set current, keeps the STM tip-sample separation fixed. How can I measure the separation?
    When we carry out spectroscopy measurement, at first we stop STM. At that time the sample bias and tunneling set current keeps the tip-sample separation constant. As soon as we do the I-V measurement the feedback loop is switched off and the voltage sweeps across the range and corresponding tunneling current is recorded. If you change the sample bias or set current tip-sample separation changes accordingly. So, how can I measure this tip-sample separation?
  • Tanya Dahms added an answer:
    Our AFM does not seem to be working.
    We have an AFM/STM from Veeco. It was working fine but a few days ago we purchased a vibration proof table for it. When it was installed the AFM did not working. It shows a message saying "Invalid floating point operation". Can anyone help us to sort out this problem.
    Tanya Dahms · University of Regina
    Yes, computer. I agree with Peter - contact Bruker - they should be helpful. Good luck!
  • Jagadish Chandra Mahato asked a question:
    During Current-Voltage measurement, the sample bias and the set current, keeps the stm tip-sample separation fixed. How can I measure the separation?
    Actually when we are to carry out spectroscopy measurement, at first we stop STM. At that time the sample bias and tunneling set current keeps the tip-sample separation constant. As soon as we do the I-V measurement the feedback loop is switched off and the voltage sweeps across the range and corresponding tunneling current is recorded. If you change the sample bias or set current tip-sample separation changes accordingly. So, how can I measure this tip-sample separation?
  • Yabin Chen asked a question:
    Is there any simple method to know the Eii value of SWNTs, and the tubes are grown on the surface by CCVD?
    Eii value is one of the most important constant of SWNTs. Normally it can be obtained by RRS and low temperature STM. Are there any other methods?
  • Raphaël Lévy asked a question:
    Are they stripy... or not?
    We published on Friday an article questioning the evidence for the existence of stripy nanoparticles (http://raphazlab.wordpress.com/2012/11/23/stripy-nanoparticles-revisited/). It would be nice to have STM/SPM experts looking at this controversy.

About Scanning Tunneling Microscopy

A scanning tunneling microscope (STM) is an instrument for imaging surfaces at the atomic level.

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