Forums
Bruker Media
Community Media
Bruker AFM Probes
SPM Digest
Application Notes
NanoTheater
Website
中文
Brochures & Datasheets
Publications
Probes Catalog
Events
Manuals & Documentation
Presentations
Guide to AFM Modes
News
Journal Club
Webinars & Video
Nanovations
Other
Dear Dave,
Let me try adressing your two questions:\
Q 1: "1. Do I have the correct equipment loaded on the machine?"
I am not sure what you mean by that. If you are asking if you can perform STM experiments on HOPG using cut metallic STM the answer is "Yes". If you are trying to visualize steps on graphite, the large scanner should just do fine. If you are attempting atomic resolution imaging you may want to use the 5um small range scanner.
Q2: "2. What are a good set of values to begin imaging? Rate? SetP? Gain? Samp Bias? Tip Bias?"
What are you trying to achieve? If you are attempting e.g. to image steps or maybe some deposits on graphite you would basically follow similar procedures for adjusting your PI gains and scan rate as you do for basic AFM imaging, i.e. a scan rate of 1 Hz might be a good value to start with a bias of around 100mV and a tunneling current of 1nA. It is always a good idea, especially if you have never done this, to verify that the bias voltage is present between tip and sample using an external multimeter. This make sure that your tip is inserted correctly, the sample is connected, and your system is putting the right voltage out. If you are attempting atomic resolution you may want to run really low PI gains and higher scan rates. This way all your information will be in the tunneling current and not the height/topography channel. The high scan rate will help keeping the effects of drift to a minimum. You can try adjusting the tunneling current up or down and adjusting your bias voltage to change the tunneling conditions to your liking.
All the Best,
Stefan
Thanks Dave for posting my question and thanks Stefan for the answer.
I went ahead and installed the 5u scanner and followed the instructions in the manual for taking an atomic resolution image. All I get is random noise when viewing the error signal. Is there a newbie guide on how to get started? Any troubleshooting tips?
Remote troubleshooting via this medium is not that easy so I am trying to establish that i) the instrument works and ii) you are doing the right things. 'Random noise" can have a lot reason from not being in feedback to a bad sample and so forth.
1. When you use the large range scanner are you able to get "good" images?
2. Have you have had any factory training on the instrument or are you attempting to learn it by yourself?
3. Where is the instrument located, e.g. is it on an airtable or similar, quite or noisy lab, fans blowing, temperature stability?
4. When was the last time you used the 5 um scanner?
5. Did you cleave the graphite? What type of graphite are you using?
6. After going into feedback, how does your tunneling signal looks like? Is it "lively" meaning it fluctuates and reacts e.g. to sound or is it jumping up and down? How is your z-piezo position?
7. When you try taking a 1um image (before attempting atomic resolution) do you get reasonable stable imaging? Can you see steps? Scan at maybe 1 Hz with the PI well adjusted
If we can not solve it here then it may be beneficial to contact Bruker customer support to work with you.
1. I was able to get reasonably good images using the large area scanner in tapping mode. (spin coat graphitic oxide) Reasonably good as far as I can tell. No good images in STM mode, however.
2. No factory training. Everything has been learning on my own and asking questions to various people.
3. Yes, it is on an air table, the lab is noisy, there are fans blowing, and the temperature is not stable. The machine is located on an exterior wall.
4. Up until this point, I've only used the large area scanner for my AFM measurements. I have never used the small area scanner.
5. I used tape on the graphite then used lab air to blow away the parts that were loosly attached. I am using Mounted HOPG (APCS-0200).
6. How do I know it goes into feedback? Yes, the signal is lively; no two consecutive traces resemble each other in any way. Z-piezo position?
7. No. No.
I've managed to get some pictures off the machine. Any idea what is going on?
http://img62.imageshack.us/g/01250009.png/
large area scan: 01250009, 0125000B, 01260010small area scan: 01260021, 01260022
Thanks!
3. Noisy lab is probably not helping with the atomic resolution. Can you move somewhere else or try measuring in the off hours? Put a big cardboard box over the system. (I know this looks ugly but has saved me numerous times in the past)
5. There shouldnt be any loose particles after peeling. If that is the case you are either not peeling right or something is wrong with your graphite sample.
6. Change the setpoint, e.g. The system should respond accordingly. It actually looks like you are seeing some steps but the current seems to jump. This may be an indication for a bad tip. Are you using PtIr tips? Did you try to re-cut them? Are they inserted firmly into the tip holder?
2. It may be benefical to contact customer support and ask for a quote for training if that is at all possible.