【求助】HRTEM分辨率

这个也太神了吧，只能恭喜你机器自动升级为含球差校正器的电镜了。

欠焦偏离Scherzer defocus，使衬度传递函数上的通道向高频端移动。
转贴一个介绍高分辨欠焦的文章。http://www.maxsidorov.com/ctfexplorer/science/defocus.htm
附件里是作者写的计算CTF的小软件，免费。
ctf

The presence of zeros in CTF means that we have gaps in the output signal. Obviously, the best CTF is the one with the fewest zeros and with the broadest band of good transmittance (where CTF is close to -1).

Back in 1949 Scherzer suggested an optimum defocus condition which occurs at:

The presence of zeros in CTF means that we have gaps in the output signal. Obviously, the best CTF is the one with the fewest zeros and with the broadest band of good transmittance (where CTF is close to -1).
this value is now called "1 scherzer".
Note: sometimes the value of 1.2 scherzer is called "Scherzer defocus" (we are going to call the value of 1.2 scherzer as "extended scherzer" throughout this manual). "Extended scherzer" provides even broader band of transmittance with CTF still close enough to -1.
Figures below show CTF's for different defoci values for a 200 keV microscope.
(Blue curve: CTF, Orange curve: combined damping envelopes).

Defocus: 1 scherzer ("True" Scherzer defocus)


Defocus: 1.2 scherzer ("Extended" Scherzer defocus). In general, this is the best defocus to take HR-TEM images.


Defocus: 1.9 scherzer ("2nd Passband" defocus). Produces a nice and broad passband which starts NOT at zero. CTF is positive so that it produces a negative phase contrast ("white atoms")


Defocus: 0.4 scherzer ("Minimum Contrast" defocus).


Defocus: 0 (low contrast, not good). Note: Zero-defocus images are NOT "Minimum Contrast" images. Minimum contrast occurs at about 0.4 scherzer (shown above).


Defocus: 10 scherzer (large and generally not good for HR-TEM)

谢谢，不过这个应该还是不能解释
在最优的欠焦条件下（估计就是1.2个舒则尔欠焦），仍然不能达到0.14 nm，此时应该在0.19 nm左右。 （对于2010 UHR）


[quote]原文由 drizzlemiao 发表:欠焦偏离Scherzer defocus，使衬度传递函数上的通道向高频端移动。
转贴一个介绍高分辨欠焦的文章。http://www.maxsidorov.com/ctfexplorer/science/defocus.htm
附件里是作者写的计算CTF的小软件，免费。
ctf

应该可以的吧

我的意思是你的实际欠焦不是1.2Scherzer。这种情况在实验中经常出现，尤其是早年仪器性能不好的时候，分辨率很高的晶格像已经大量出现了。通常仪器的额定点分辨率是按1.2Scherzer给的，那是默认的最佳欠焦。

嗯，通过欠焦量的变化，达到更高的分辨率，应该是这种情况了。

可能是非线性成像原理导致的

2010UHR的点分辨率为0.19nm，但点阵分辨率为0.14nm，使用高欠焦值成像可能会观察到0.14nm的结构细节，只不过这些细节不能直接解释，必须进行图像处理或图像模拟。可以用多层法先算一下。

不正确的欠焦量导致的错误信息。