等離子體電子可用于制備金屬薄膜

等離子體電子可用于制備金屬薄膜

The processors used in today's computers and phones consist of billions of tiny transistors connected by thin metallic films. Scientists at Linköping University, LiU, have now shown that it is possible to create thin films of metals by allowing the free electrons in a plasma take an active role. A plasma forms when energy is supplied that tears away electrons from the atoms and molecules in a gas, to produce an ionised gas. In our everyday life, plasmas are used in fluorescent lamps and in plasma displays. The method developed by the LiU researchers using plasma electrons to produce metallic films is described in an article in the Journal of Vacuum Science & Technology.

當今計算機和電話中使用的處理器，由數(shù)十億個由金屬薄膜連接的微型晶體管組成。林克平大學(xué)的科學(xué)家們現(xiàn)在已經(jīng)證明，允許等離子體中的自由電子發(fā)揮積極作用，就有可能創(chuàng)造出金屬薄膜。當能量從氣體中的原子和分子中分離出電子，產(chǎn)生電離氣體時，等離子體就形成了。在我們的日常生活中，等離子體被用于熒光燈和等離子顯示器。在《真空科學(xué)與技術(shù)》雜志上發(fā)表的一篇文章中描述了劉研究員利用等離子體電子制備金屬薄膜的方法。

"We can see several exciting areas of application, such as the manufacture of processors and similar components. With our method it is no longer necessary to move the substrate on which the transistors are created backwards and forwards between the vacuum chamber and a water bath, which happens around 15 times per processor," says Henrik Pedersen, professor of inorganic chemistry in the Department of Physics, Chemistry and Biology at Linköping University.

“我們可以看到一些令人興奮的應(yīng)用領(lǐng)域，例如處理器和類似組件的制造。”林克平大學(xué)物理、化學(xué)和生物系無機化學(xué)教授Henrik Pedersen說：“用我們的方法，不再需要在真空室和水浴之間來回移動產(chǎn)生晶體管的基底，每個處理器大約15次。”。

A common method of creating thin films is to introduce molecular vapours containing the atoms that are required for the film into a vacuum chamber. There they react with each other and the surface on which the thin film is to be formed. This well-established method is known as chemical vapour deposition (CVD). In order to produce films of pure metal by CVD, a volatile precursor molecule is required that contains the metal of interest. When the precursor molecules have become absorbed onto the surface, surface chemical reactions involving another molecule are required to create a metal film. These reactions require molecules that readily donate electrons to the metal ions in the precursor molecules, such that they are reduced to metal atoms, in what is known as a "reduction reaction." The LiU scientists instead turned their attention to plasmas.

制作薄膜的一種常用方法是將含有薄膜所需原子的分子蒸汽引入真空室。在那里，它們相互作用，形成薄膜的表面。這種公認的方法被稱為化學(xué)氣相沉積(CVD)。為了用化學(xué)氣相沉積法制備純金屬薄膜，需要一種含有感興趣金屬的揮發(fā)性前體分子。當前體分子被吸附到表面時，需要與另一分子發(fā)生表面化學(xué)反應(yīng)來形成金屬膜。這些反應(yīng)要求分子能夠很容易地將電子貢獻給前體分子中的金屬離子，這樣它們就被還原成金屬原子，這就是所謂的“還原反應(yīng)”。林克平大學(xué)的科學(xué)家們轉(zhuǎn)而將注意力轉(zhuǎn)向等離子體。

"We reasoned that what the surface chemistry reactions needed was free electrons, and these are available in a plasma. We started to experiment with allowing the precursor molecules and the metal ions to land on a surface and then attract electrons from a plasma to the surface," says Henrik Pedersen.

“我們推斷表面化學(xué)反應(yīng)所需要的是自由電子，而這些電子在等離子體中是可用的。我們開始試驗讓前體分子和金屬離子降落在一個表面上，然后將電子從等離子體吸引到表面上。”Henrik Pedersen說。

Researchers in inorganic chemistry and in plasma physics at IFM have collaborated and demonstrated that it is possible to create thin metallic films on a surface using the free electrons in an argon plasma discharge for the reduction reactions. In order to attract the negatively charged electrons to the surface, they applied a positive potential across it.

IFM無機化學(xué)和等離子體物理的研究人員，已經(jīng)合作并證明了利用氬等離子體放電中的自由電子在表面上產(chǎn)生金屬薄膜的可能性。為了把帶負電的電子吸引到表面，他們在表面上施加了正電位。

The study describes work with non-noble metals such as iron, cobalt and nickel, which are difficult to reduce to metal. Traditional CVD has been compelled to use powerful molecular reducing agents in these cases. Such reducing agents are difficult to manufacture, manage and control, since their tendency to donate electrons to other molecules makes them very reactive and unstable. At the same time, the molecules must be sufficiently stable to be vaporised and introduced in gaseous form into the vacuum chamber in which the metallic films are being deposited.

這項研究描述了對鐵、鈷和鎳等非貴金屬的研究，這些金屬很難還原成金屬。在這些情況下，傳統(tǒng)的化學(xué)氣相沉積法不得不使用強大的分子還原劑。這種還原劑很難制造、管理和控制，因為它們向其他分子提供電子的傾向使它們非?；顫姾筒环€(wěn)定。同時，這些分子必須足夠穩(wěn)定，以便汽化并以氣態(tài)形式引入正在沉積金屬薄膜的真空室。

"What may make the method using plasma electrons better is that it removes the need to develop and manage unstable reducing agents. The development of CVD of non-noble metals is hampered due to a lack of suitable molecular reducing agents that function sufficiently well," says Henrik Pedersen.

“可能使使用等離子體電子的方法更好的原因是，它消除了開發(fā)和處理不穩(wěn)定還原劑的需要。由于缺乏合適的分子還原劑，它們無法充分發(fā)揮功能，非貴金屬化學(xué)氣相沉積的開發(fā)。” Henrik Pedersen說。

The scientists are now continuing with measurements that will help them understand and be able to demonstrate how the chemical reactions take place on the surface where the metallic film forms. They are also investigating the optimal properties of the plasma. They would also like to test different precursor molecules to find ways of making the metallic films purer.

科學(xué)家們現(xiàn)在正在繼續(xù)進行測量，這將有助于他們理解并能夠證明化學(xué)反應(yīng)是如何在金屬薄膜形成的表面發(fā)生的。他們也在研究等離子體的最佳特性。他們還想測試不同的前體分子，以找到使金屬薄膜更純凈的方法。

The research has obtained financial support from the Swedish Research Council, and has been carried out in collaboration with Daniel Lundin, guest professor at IFM.

這項研究得到了瑞典研究委員會的資助，并與IFM客座教授Daniel Lundin合作進行。