From jwc at snf.stanford.edu Fri Mar 11 09:51:38 2011 From: jwc at snf.stanford.edu (James W. Conway) Date: Fri, 11 Mar 2011 09:51:38 -0800 Subject: Dealing with noisy SEM pictures In-Reply-To: References: Message-ID: <4D7A612A.3080203@snf.stanford.edu> Hello Karthik, Sounds like it may be just part of getting used to the very broad parameter space on this system as a new user. Users whom are working at low voltage (<10 keV acceleration voltage) or seeking ultra high resolution may have switched the movable aperture strip to the smallest hole size. (No 4) This reduces the beam current and hence the signal to noise ratio increases. It is important too that you continue to use the proper emission level. (currently set to 12 uA) It is quite normal for emission to fall off this setting requiring users to periodically press 'HV On' button which then increases the extraction voltage in 100 V steps until it reaches the correct set point of emission level. Ultimately you will reach 6.5 kV extraction voltage and you will then need to turn off the HV and perform the flashing operation on the tip. In normal extended usage over hours of time the emission stabilizes and you may not have to reset HV as often. Now once you have obtained the proper 10 - 12 uA emission you can further improve your imaging noise level by careful adjustments of brightness and contrast using either the waveform function (monitor button next to the ABC+MON control on left side of the key board. Be sure to not have the CRT screen brightness on the monitor set too high as well. Contrast is the amplifier for the SE detector and brightness is CRT display screen amplifier. Too much contrast and you will readily see shot noise from the detector. Finally if you still cannot see a suitable image switch to hole No 3 on the aperture strip and then realign the column settings using PF3. It should reduce to signal to noise ratio greatly. Currently we are planning to perform a column PM routine and will be cleaning up several items with the stage as well as replace the FE gun tip, apertures, and SE detector phosphor scintillator. These step will also greatly improve brightness and all Users should see some marked improvement in resolution and reduced noise from the detectors and amplifiers.... If you have further questions please see me during my office hours. Thank you for an excellent question that I may make a FAQ from. James Conway On 3/9/2011 2:50 PM, Karthik Balakrishnan wrote: > Hi James, > > I brought a few samples in yesterday to examine the carbide thin films > using the 4160 SEM. I was getting very noisy pictures and was > wondering if you had any suggestions on how to deal with the issue. I > will be performing nanoindentation on the samples and want to make > sure that the features don't just get lost in the noise. It's an > aluminum substrate so maybe that's part of the issue? > > -Karthik From jwc at snf.stanford.edu Wed Mar 30 09:39:04 2011 From: jwc at snf.stanford.edu (James W. Conway) Date: Wed, 30 Mar 2011 09:39:04 -0700 Subject: New Policies on usage of ESPACER conductive Polymer -- Apply on the HEADWAY2 coater only. Message-ID: <4D935CA8.8090403@snf.stanford.edu> An HTML attachment was scrubbed... URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: starheader.gif Type: image/gif Size: 4449 bytes Desc: not available URL: