2016年考研英语阅读材料:Display screens

　　LIQUID-CRYSTAL displays are a familiar and ubiquitous technology. But if Harish Bhaskaran of Oxford University is right, their days may be numbered. The essential feature of LCDs is that the pixels in them switch between amorphous and crystal-like phases, which changes their optical properties. In a paper in this week's Nature, Dr Bhaskaran and his colleagues describe something similar in a solid material. At the least, that would stop the messy abstract-impressionist patterns which happen when an LCD is dropped too hard. At most, it might open up a new range of applications, from clothes that change colour to dimmable windscreens.

　　Solid phase-change materials are already used to store data in optical memory disks. They are also being considered for use in memory chips, because the switch between amorphous and crystalline states alters their electrical properties in ways that can store electronic bits of data. Dr Bhaskaran, though, has shown that thin enough films of the right sort of material can be made to change colour, too.

　　This property would make them suitable both for displays that rely on reflected light (so-called electronic paper) and the older, backlit sort that rely on transmitted light. The resulting displays would be thin and could be flexible if printed on the right material―increasing the range of applications they might be used in. And they would consume little power, since energy need be used only when a pixel has to be flipped from one phase to another.

　　The researchers' material of choice is an alloy of germanium, antimony and tellurium. Both the crystalline and the amorphous phases of this substance are stable at any temperature a device is likely to experience, and thin films of it are more or less transparent. The power needed to effect the phase change could be fed to individual pixels by electrodes made of indium tin oxide, which is also transparent.

　　The colour of a pixel would depend not only on its phase, but also on its thickness, which would affect the way light waves being reflected within it interfere with one another, cancelling out some frequencies while amplifying others. (The effect is similar to the creation of colours by a thin layer of oil on a puddle.) Generally, the alloy layer needs to be thinner than 20 nanometres for that to happen.

　　To demonstrate their idea, the researchers sprayed films of their alloy onto pieces of silicon, quartz and plastic. They then used a device called an atomic-force microscope, which has a tip a few nanometres across, to apply appropriate electric currents in a grid pattern across the film's surface. This grid mimicked an array of pixels, creating a stable pattern. The result, as their picture of a Japanese wave shows, is a recognisable image―if not, yet, a perfect one.

　　Adding the indium-tin-oxide electrodes is a more #plicated process, but to show it can be done in principle, Dr Bhaskaran has made a single pixel this way. Whether his idea will get off the lab bench and into the shops remains to be seen. It is by no means the only suggestion around for a new generation of display screens. But it looks plausible.

　　参考译文:

　　液晶显示屏是一项成熟而广泛应用的技术。但如果牛津大学的Harish Bhaskaran的想法实现，液晶屏的好景也就没几天了。LCD的基本特征是其像素在非晶相和类晶相间转化，因此改变其光学性质。在本周的《自然》杂志上，Bhaskaran博士及其同事陈述了一种类似的固体材料。至少该材质可以防止当LCD猛烈坠地后产生麻烦的抽象印象派图案。最理想情况下，它会有新的应用范围，从变色布料到可调光挡风玻璃。

　　固态相变材料已经用于在光储存盘中储存数据。也可能被用于记忆芯片，因为其非晶态和晶态之间的转变也改变了其电学性能，因此他们能储存电子数据。然而，Bhaskaran博士展示了一种特定材料膜，在足够薄的情况下也可以改变颜色。

　　这一性能将使其适合于反射光显示(所谓电子纸)和早期的依赖透射光的背光显示。所得显示屏不仅薄，而且铺在合适材料上时非常灵活，增加了其应用范围。而且它消耗的功率更少，因为这种材料只需要在变相的时候消耗能量。

　　研究人员选择的材料是镓、锑和碲合金。这一物质的晶态和非晶态在任何设备适用温度下都很稳定。其薄膜也几乎透明。要激发相转变所需的能量可以由透明的铟锡氧化物电极向单个像素提供。

　　单个像素的颜色不仅取决于其相态，也同其厚度有关。厚度会影响光波在两个像素间界面处的反射，削弱部分频率，加强其他频率。(此效应类似于池塘表面薄油层产生的色彩。)一般来说，合金层需要薄于20 nm才会发生这一现象。

　　为了证明其观点，研究人员将其合金铺覆到硅，石英和塑料上。然后他们使用所谓原子力显微镜的设备来施加合适的电流在横穿膜表面的网格上。原子力显微镜尖端仅有几个纳米大小。网格模仿像素排列，产生稳定的模式。他们对日本电波的拍摄结果是一个可识别的图像，即便不可识别，也是非常完美的。

　　加入铟锡氧化物电极是更为复杂的过程，但是可以从原理上展示其过程。Bhaskaran用这种方式制备了单个像素。他的想法能否从实验室走进商用还是未知。这绝不是新一代显示屏的唯一方案，但颇得看好。