| 查看: 1828 | 回复: 21 | |||
nanolab289银虫 (小有名气)
|
[交流]
【求助】30金币求助翻译贴内内容 已有17人参与
|
|
The scanning electron microscope (SEM) is a type of electron microscope that images the sample surface by scanning it with a high-energy beam of electrons in a raster scan pattern. The electrons interact with the atoms that make up the sample producing signals that contain information about the sample's surface topography, composition and other properties such as electrical conductivity. The types of signals produced by an SEM include secondary electrons, back scattered electrons (BSE), characteristic x-rays, light (cathodoluminescence), specimen current and transmitted electrons. These types of signal all require specialized detectors for their detection that are not usually all present on a single machine. The signals result from interactions of the electron beam with atoms at or near the surface of the sample. In the most common or standard detection mode, secondary electron imaging or SEI, the SEM can produce very high-resolution images of a sample surface, revealing details about 1 to 5 nm in size. Due to the way these images are created, SEM micrographs have a very large depth of field yielding a characteristic three-dimensional appearance useful for understanding the surface structure of a sample. A wide range of magnifications is possible, ranging from about x 25 (about equivalent to that of a powerful hand-lens) to about x 250,000, about 250 times the magnification limit of the best light microscopes. Back-scattered electrons (BSE) are beam electrons that are reflected from the sample by elastic scattering. BSE are often used in analytical SEM along with the spectra made from the characteristic x-rays. Because the intensity of the BSE signal is strongly related to the atomic number (Z) of the specimen, BSE images can provide information about the distribution of different elements in the sample. For the same reason BSE imaging can image colloidal gold immuno-labels of 5 or 10 nm diameter, that would otherwise be difficult or impossible to detect in secondary electron images in biological specimens. Characteristic X-rays are emitted when the electron beam removes an inner shell electron from the sample, causing a higher energy electron to fill the shell and release energy. These characteristic x-rays are used to identify the composition and measure the abundance of elements in the sample. [ Last edited by nanolab289 on 2010-9-7 at 11:45 ] |
回复此楼» 猜你喜欢
Renlab@monash全奖博士机会，最后三天！
已经有0人回复
-
今年面上没有消息，想来是没了，散个金攒攒人品，为明年祈福
已经有698人回复
-
物理化学论文润色/翻译怎么收费?
已经有246人回复
-
合肥工业大学854仪器技术综合专业课考研
已经有0人回复
-
27年电化学博士毕业，想找海外QS前50的高校读博后求推荐
已经有3人回复
-
27年电池/材料类博士申请
已经有2人回复
-
2027年博士申请或转博科研助理 求推荐
已经有1人回复
-
请问谁有2025最新影响因子Excel表？金币求助！
已经有53人回复
-
氯化钠与有机磺酸分离
已经有0人回复
» 本主题相关价值贴推荐，对您同样有帮助:
- 专业外语版版规
已经有15人回复
- ◆○◆○【外语学习版版规】（2017版）○◆○◆
已经有120人回复
- ★★★★★论文翻译版求助者必读★★★★★
已经有13人回复
- 求助者必读------公示2周，欢迎提出意见或建议！！！
已经有31人回复
- 翻译互助版规（求助前请务必仔细阅读，谢谢！）
已经有34人回复
- 科研工具版新版规（2008整合修订版）
已经有123人回复
nanolab289
银虫 (小有名气)
- 应助: 0 (幼儿园)
- 金币: 185.1
- 散金: 100
- 红花: 1
- 帖子: 75
- 在线: 77.1小时
- 虫号: 541486
- 注册: 2008-04-08
- 专业: 金属功能材料
该段内容以2金币答谢
nanolab289:编辑内容 2010-09-07 11:46
|
In a typical SEM, an electron beam is thermionically emitted from an electron gun fitted with a tungsten filament cathode. Tungsten is normally used in thermionic electron guns because it has the highest melting point and lowest vapour pressure of all metals, thereby allowing it to be heated for electron emission, and because of its low cost. Other types of electron emitters include lanthanum hexaboride (LaB6) cathodes, which can be used in a standard tungsten filament SEM if the vacuum system is upgraded and field emission guns (FEG), which may be of the cold-cathode type using tungsten single crystal emitters or the thermally-assisted Schottky type, using emitters of zirconium oxide. 完成该部分内容以2个金币答谢. [ Last edited by nanolab289 on 2010-9-7 at 11:46 ] |
2楼2010-08-18 15:33:59
nanolab289
银虫 (小有名气)
- 应助: 0 (幼儿园)
- 金币: 185.1
- 散金: 100
- 红花: 1
- 帖子: 75
- 在线: 77.1小时
- 虫号: 541486
- 注册: 2008-04-08
- 专业: 金属功能材料
nanolab289:编辑内容 2010-09-07 11:46
|
The electron beam, which typically has an energy ranging from a few hundred eV to 40 keV, is focused by one or two condenser lenses to a spot about 0.4 nm to 5 nm in diameter. The beam passes through pairs of scanning coils or pairs of deflector plates in the electron column, typically in the final lens, which deflect the beam in the x and y axes so that it scans in a raster fashion over a rectangular area of the sample surface.--------------------------- 完成此段内容以3个金币答谢 [ Last edited by nanolab289 on 2010-9-7 at 11:46 ] |
3楼2010-08-18 15:35:00
 |
4楼2010-08-18 16:02:11
xiaoxiaote
金虫 (正式写手)
- 应助: 1 (幼儿园)
- 金币: 783.2
- 散金: 511
- 红花: 2
- 帖子: 442
- 在线: 40.5小时
- 虫号: 888264
- 注册: 2009-10-30
- 专业: 电化学
5楼2010-08-18 17:22:05
fengqiu3160
金虫 (正式写手)
- ECEPI: 1
- 应助: 0 (幼儿园)
- 金币: 1915.4
- 散金: 9
- 帖子: 445
- 在线: 67.3小时
- 虫号: 1006985
- 注册: 2010-04-27
- 专业: 电化学
6楼2010-08-18 17:23:42
hu64191423
金虫 (正式写手)
- 应助: 0 (幼儿园)
- 金币: 194.5
- 散金: 129
- 红花: 1
- 帖子: 865
- 在线: 47.2小时
- 虫号: 1072317
- 注册: 2010-08-10
- 专业: 电化学
7楼2010-08-18 20:00:34
daochunhan
铁杆木虫 (正式写手)
- 应助: 0 (幼儿园)
- 金币: 5321.7
- 散金: 6
- 红花: 3
- 帖子: 455
- 在线: 66.7小时
- 虫号: 388997
- 注册: 2007-06-01
- 性别: GG
- 专业: 化工热力学和基础数据
8楼2010-08-18 22:18:13
9楼2010-08-18 22:33:50
nanolab289
银虫 (小有名气)
- 应助: 0 (幼儿园)
- 金币: 185.1
- 散金: 100
- 红花: 1
- 帖子: 75
- 在线: 77.1小时
- 虫号: 541486
- 注册: 2008-04-08
- 专业: 金属功能材料
10楼2010-08-19 14:32:40
