一、電子顯微鏡的組成

電(dian)子顯微鏡(jing)由鏡(jing)筒、真(zhen)空裝置和電(dian)源柜三部分組成(cheng)。

1、鏡筒

主要有電(dian)(dian)子(zi)源、電(dian)(dian)子(zi)透鏡、樣(yang)品(pin)架(jia)、熒光屏和探測器等部件(jian)，這些部件(jian)通常是自上而下地裝配成一個柱體。

電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子(zi)(zi)透(tou)(tou)(tou)鏡(jing)(jing)用來聚(ju)焦(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子(zi)(zi)，是(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子(zi)(zi)顯微(wei)鏡(jing)(jing)鏡(jing)(jing)筒中(zhong)最重(zhong)要(yao)的(de)(de)(de)部件。一般(ban)使(shi)(shi)用的(de)(de)(de)是(shi)磁透(tou)(tou)(tou)鏡(jing)(jing)，有時(shi)也有使(shi)(shi)用靜(jing)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)透(tou)(tou)(tou)鏡(jing)(jing)的(de)(de)(de)。它用一個對稱于(yu)鏡(jing)(jing)筒軸(zhou)線(xian)的(de)(de)(de)空間(jian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)場(chang)或磁場(chang)使(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子(zi)(zi)軌(gui)跡向(xiang)軸(zhou)線(xian)彎曲(qu)形(xing)成(cheng)聚(ju)焦(jiao)，其作用與光(guang)(guang)學顯微(wei)鏡(jing)(jing)中(zhong)的(de)(de)(de)光(guang)(guang)學透(tou)(tou)(tou)鏡(jing)(jing)（凸透(tou)(tou)(tou)鏡(jing)(jing)）使(shi)(shi)光(guang)(guang)束聚(ju)焦(jiao)的(de)(de)(de)作用是(shi)一樣(yang)的(de)(de)(de)，所以(yi)(yi)(yi)稱為電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子(zi)(zi)透(tou)(tou)(tou)鏡(jing)(jing)。光(guang)(guang)學透(tou)(tou)(tou)鏡(jing)(jing)的(de)(de)(de)焦(jiao)點(dian)是(shi)固定的(de)(de)(de)，而電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子(zi)(zi)透(tou)(tou)(tou)鏡(jing)(jing)的(de)(de)(de)焦(jiao)點(dian)可(ke)以(yi)(yi)(yi)被調節，因此(ci)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子(zi)(zi)顯微(wei)鏡(jing)(jing)不(bu)像(xiang)光(guang)(guang)學顯微(wei)鏡(jing)(jing)那(nei)樣(yang)有可(ke)以(yi)(yi)(yi)移動的(de)(de)(de)透(tou)(tou)(tou)鏡(jing)(jing)系統。現(xian)代電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子(zi)(zi)顯微(wei)鏡(jing)(jing)大多(duo)采(cai)用電(dian)(dian)(dian)(dian)(dian)(dian)(dian)磁透(tou)(tou)(tou)鏡(jing)(jing)，由很穩(wen)(wen)定的(de)(de)(de)直流勵磁電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流通過(guo)帶極靴的(de)(de)(de)線(xian)圈產(chan)生的(de)(de)(de)強(qiang)磁場(chang)使(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子(zi)(zi)聚(ju)焦(jiao)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子(zi)(zi)源(yuan)是(shi)一個釋放自(zi)由電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子(zi)(zi)的(de)(de)(de)陰極，柵極，一個環狀加(jia)速電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子(zi)(zi)的(de)(de)(de)陽極構成(cheng)的(de)(de)(de)。陰極和陽極之(zhi)(zhi)間(jian)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)差必(bi)須非常高，一般(ban)在(zai)數千伏到(dao)3百萬伏特之(zhi)(zhi)間(jian)。它能發射并形(xing)成(cheng)速度均勻的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子(zi)(zi)束，所以(yi)(yi)(yi)加(jia)速電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)(de)穩(wen)(wen)定度要(yao)求不(bu)低(di)于(yu)萬分之(zhi)(zhi)一。

樣(yang)品(pin)可以穩定地(di)放在樣(yang)品(pin)架上，此外往往還有可以用來改變樣(yang)品(pin)（如移動、轉動、加熱、降溫、拉(la)長等）的裝置(zhi)。

探測器用來收集電子的信(xin)(xin)號(hao)或(huo)次級信(xin)(xin)號(hao)。

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2、真空裝置

用以保(bao)障顯微鏡內的真(zhen)(zhen)空狀態(tai)，這樣電子在其(qi)路徑上不會被吸(xi)收或偏向，由機械真(zhen)(zhen)空泵(beng)、擴散泵(beng)和真(zhen)(zhen)空閥門等構成，并通過抽氣管道與鏡筒相聯接。

3、電源柜

由高壓發生器、勵磁電流穩流器和各種調節控制單元組成。

二、電子顯微鏡如何進行樣本處理

1、固定：為了盡(jin)量保(bao)存(cun)樣本的(de)原(yuan)樣使用戊二(er)醛(quan)來(lai)硬化樣本和(he)使用鋨(e)酸來(lai)染色(se)脂肪。

2、冷固定：將樣本放在液態(tai)的乙烷中速凍，這樣水不會(hui)結晶(jing)，而(er)形成非(fei)晶(jing)體的冰。這樣保存的樣品(pin)損壞比較(jiao)小(xiao)，但圖像的對比度非(fei)常(chang)低。

3、脫干：使用乙醇和丙酮來取代水(shui)。

4、墊入(ru)：樣(yang)本被墊入(ru)后可以分割。

5、分割：將樣本(ben)使用金剛石刃切成薄片。

6、染色(se)：重的原子(zi)如鉛或鈾比輕的原子(zi)散(san)射電子(zi)的能力高，因此(ci)可被用(yong)來提高對(dui)比度(du)。