等离子体电子可用于制备金属薄膜
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.
当今计算机和电话中使用的处理器，由数十亿个由金属薄膜连接的微型晶体管组成。林克平大学的科学家们现在已经证明，允许等离子体中的自由电子发挥积极作用，就有可能创造出金属薄膜。当能量从气体中的原子和分子中分离出电子，产生电离气体时，等离子体就形成了。在我们的日常生活中，等离子体被用于荧光灯和等离子显示器。在《真空科学与技术》杂志上发表的一篇文章中描述了刘研究员利用等离子体电子制备金属薄膜的方法。
"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.
“我们可以看到一些令人兴奋的应用领域，例如处理器和类似组件的制造。”林克平大学物理、化学和生物系无机化学教授Henrik Pedersen说：“用我们的方法，不再需要在真空室和水浴之间来回移动产生晶体管的基底，每个处理器大约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.
制作薄膜的一种常用方法是将含有薄膜所需原子的分子蒸汽引入真空室。在那里，它们相互作用，形成薄膜的表面。这种公认的方法被称为化学气相沉积(CVD)。为了用化学气相沉积法制备纯金属薄膜，需要一种含有感兴趣金属的挥发性前体分子。当前体分子被吸附到表面时，需要与另一分子发生表面化学反应来形成金属膜。这些反应要求分子能够很容易地将电子贡献给前体分子中的金属离子，这样它们就被还原成金属原子，这就是所谓的“还原反应”。林克平大学的科学家们转而将注意力转向等离子体。
"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.
“我们推断表面化学反应所需要的是自由电子，而这些电子在等离子体中是可用的。我们开始试验让前体分子和金属离子降落在一个表面上，然后将电子从等离子体吸引到表面上。”Henrik Pedersen说。
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无机化学和等离子体物理的研究人员，已经合作并证明了利用氩等离子体放电中的自由电子在表面上产生金属薄膜的可能性。为了把带负电的电子吸引到表面，他们在表面上施加了正电位。
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.
这项研究描述了对铁、钴和镍等非贵金属的研究，这些金属很难还原成金属。在这些情况下，传统的化学气相沉积法不得不使用强大的分子还原剂。这种还原剂很难制造、管理和控制，因为它们向其他分子提供电子的倾向使它们非常活泼和不稳定。同时，这些分子必须足够稳定，以便汽化并以气态形式引入正在沉积金属薄膜的真空室。
"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.
“可能使使用等离子体电子的方法更好的原因是，它消除了开发和处理不稳定还原剂的需要。由于缺乏合适的分子还原剂，它们无法充分发挥功能，非贵金属化学气相沉积的开发。” Henrik Pedersen说。
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.
科学家们现在正在继续进行测量，这将有助于他们理解并能够证明化学反应是如何在金属薄膜形成的表面发生的。他们也在研究等离子体的最佳特性。他们还想测试不同的前体分子，以找到使金属薄膜更纯净的方法。
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.
这项研究得到了瑞典研究委员会的资助，并与IFM客座教授Daniel Lundin合作进行。
