These days we automatically associate computers and various mobile devices with chips made of semiconducting transistors. Indeed for many years the transistor has been a ubiquitous electronic component.
However, this was not always the case. In the past, devices called vacuum tubes, or valves were used in electronic devices.
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Transistors vs. vacuum tubes/valves
A transistor is a binary device which acts as a switch, either preventing or allowing a current to flow. Transistors can also be used to amplify signals. They are made from semiconductor material.
A vacuum tube is also capable of controlling current flow but achieves this using a different mechanism to the transistor. They are also much larger than transistors.
Basically, after the introduction of transistors, the electronics industry took off at a phenomenal pace. This has been possible due to their continual shrinking thanks to design and technological advances.
To emphasize this, modern electronic devices contain literally billions of transistors, and they are fit into relatively small packages.
As the numbers of transistors in devices has increased over the years, so has the processing power and capabilities of these devices.
In short, transistors and other semiconductor-based electronics are awesome. You should note, however, that they are not without their issues. Due to the properties of semiconducting materials, the flow of electrons is limited somewhat, which can hamper devices from performing as ideally as one would want.
Note: These devices could lead to all kinds of exciting tech such as better solar cells and could even be used outside of the electronics industry in areas such as photochemistry and photocatalysis maybe being useful even in various environmental applications.
In these devices electrons are liberated into free space, meaning that there is no material there to limit their flow. This is great but to release these electrons, a lot of energy is usually needed as is the case with tubes/valves currently on the market today.
High temperatures/high voltage is usually required to free the electrons. This obviously isn’t necessary with semiconductor devices, and these types of conditions aren’t suitable for devices which rely on microelectronics. This is one of the many things which would have aided in the rise of semiconductor technology.
The team at UCSD, however, took a novel approach to getting around this problem. Their devices are made with what is called a metasurface made of gold, mounted on a silicon wafer with a layer of silicon dioxide sandwiched in between.
To release electrons the team use a two-fold approach; a low voltage along and a low-powered infrared laser are applied to the devices. This leads to the release of electrons which are essentially ripped from the metal due to the creation of a strong electric field after activation with the laser and voltage.
Performance and Outlook
In tests, after activation, the devices displayed a one thousand percent increase in conductivity. These devices are admittedly not perfect yet, but they were only intended as a proof-of-concept in the first place.
The team’s lead, Professor Dan Sievenpiper states that this type of device isn’t capable of replacing the entire range of semiconductor devices, but he believes that they will have their stand out areas such as in applications which require high frequencies or high power.
The team is exploring methods of improving their devices as well as getting a better understanding of how they work and exploring all of the possible applications.