As well as being our “microscopes” for unravelling the atomic structure of matter, crystals are omnipresent and play a fundamental role in our daily lives. Crystallography has enabled us to learn to manipulate the properties of crystals and use them to our benefit, this being in large part one of the pillars upon which science and technology have contributed to building the welfare state. Today our world would be inconceivable without the technology that crystals enable and provide. To prove this, we only have to look at something almost all of us carry around: a mobile telephone. And, for example, the piezoelectric effect of some crystals allows us to build devices like the sonar and ultrasounds.
|Silicon chip inside a microproce.||Monocrystalline silicon wafer with etched electronic chip.|
Every one of the little chips that make our devices work contains a small chip of semiconductor crystal with minute circuits etched on the nanometric scale that consist of between several hundred and several million electronic components.
It is quite possible that your mobile is equipped with an LCD screen. The acronym stands for “Liquid Crystal Display” and, indeed, its working is based on the light modulation properties that liquid crystals have due to the fact that they are crystals. Another screen technology is LED (“Light Emitting Diode”). In this case the image is formed by the light emitted by each pixel, which is a tiny diode of semiconductor crystal. LEDs are more and more present in everyday life, and not only in television screens and mobile phones, but also in advertising boards and even the lamps in our homes.
Telephones are increasingly equipped with sensors that make them “smarter”. They are commonly equipped with compasses, gyroscopes or accelerometers that enable them to know their orientation and movements. In time, other sensors (temperature, humidity, pressure…) will be incorporated. The technology of microelectromechanical systems (MEMS) allows micro-manufacturing on a crystalline substrate of mechanical, thermal, optical and fluidic structures, together with the electronics necessary for its operation.
All digital electronic devices (including the mobile phone) use one or more clocks to set the pace of the electronic circuitry and synchronise their operations. This clock is typically a resonance circuit based on the piezoelectric effect of a quartz crystal. In fact, the corresponding electronic component is colloquially called “crystal” and is the same found in wristwatches, computers, radios and a near-infinity of other electronic devices. The same phenomenon of piezoelectricity is also used to make other devices work, such as microphones and telephone speakers, pickups for musical instruments, sonar and medical ultrasounds.
As well as electronic and mechanical, other properties of crystals are at the basis of current technologies, such as the laser or the components of non-linear optics that enable us to generate or manipulate beams of light.
Solar energy uses silicon crystals, among other materials, and its future depends in large part on finding the cheapest way to produce compound III-V crystals.