For decades the transistors in microchips became smaller and smaller. About every two years the number of transistors on commercially available chips could be doubled - this phenomenon became known as "Moore's Law". But for some years now this has been a thing of the past. Miniaturization has reached a natural limit because, on a scale of a few nanometers, one suddenly has to contend with completely new problems.
Now, however, the next major miniaturization step could become possible - with two-dimensional (2D) materials consisting only of an atom-thick material layer. With the help of a novel insulator made of calcium fluoride, the University of Technology (TU) of Vienna has now succeeded in producing an ultra-thin transistor that has excellent electrical properties and, in contrast to previous technologies, can also be extremely reduced in size due to its low thickness.
Research on semiconductor materials, as required for the manufacture of transistors, has made great progress in recent years: In the meantime, ultra-thin semiconductors can be produced as so-called 2D materials consisting of only a few atomic layers. However, this is not enough to build an extremely small transistor. "In addition to the ultra-thin semiconductor, an ultra-thin insulator is also needed, explains Prof. Tibor Grasser from the Institute of Microelectronics at Vienna University of Technology.
This is due to the basic structure of a transistor: current can flow from one side of the transistor to the other - but only if a suitable electric field is generated in the middle by applying an electric voltage. An insulating layer is needed between the electrode that provides this field and the semiconductor itself. "There have always been transistor experiments with ultra-thin semiconductors coupled with ordinary, thicker insulators," explains Grasser. "But that is of little use - first, we cannot speak of miniaturization if the transistor, including the insulator, has a greater thickness after all, and second, it became apparent that the sensitive electronic properties of the semiconductor are disturbed by the inferior insulator surface.