Indissoluble Bond between Tungsten and Transistor

Transistors are considered to be the greatest inventions in electronic technology in the 20th century, setting off a microelectronics industry revolution and laying the foundation for a modern civil society. And since its appearance, it has kept a close relationship with tungsten. 

The invention of transistor can be traced back to 1929. At that time, the engineer, Lillian Feld obtained a patent of transistor. However, limited by the technology level, the material for producing this could not reach enough purity, so the transistor was impossible to make. In 1945, Alcatel-Lucent Bell Labs set up semiconductor research team led by W. B. Shockley. The members included the experimental physicist W. H. Brattain, G. L. Pearson, physical chemist R. Gibney, circuit expert H. Moore and theoretical physicist J. Bardeen.

Soon after the establishment of research team, members changed their research focus from the development of field-effect amplifiers to the fundamental theory of semiconductors---the study of surface states. The problem of surface state is the basis of promoting the field-effect amplifier experiment. After more than a year of experiments, in September 1947, the research team finally confirmed that the surface state effect does exist. Through the further study, they found that injecting the liquid which contains the positive and negative ions between the electrode plate and silicon crystal surface and increasing the voltage will reinforce or reduce the effect. 

On 21st November 1947, Bardeen proposed to Brattain to start a semiconductor amplifier development experiment. They conducted experiments on the same day and observed a weak amplified current signal in the output loop. But their amplifying devices have almost no voltage gain and can only operate in an ultra-low frequency of no more than 10 Hz. The amplifier must be able to amplify an input signal of several kilohertz.

On 11th December 1947, Gibney provided a N-type germanium wafer that has an oxide layer (aimed at replacing electrolyte). Five small gold particles were deposited on the oxide layer. Brattain made a small hole in the gold grain. Then, he threaded the tungsten wire through the hole and inserted it into the germanium crystal as an electrode, hoping to change the conductivity between the tungsten wire electrode and the germanium crystal by changing the voltage between the gold grain and the germanium crystal. It is found that the resistance between gold grains and germanium crystals is very small, that is, the oxide layer does not play an insulating role.

Despite this, Brattain decided to do a few experiments. In one experiment, Brattain accidentally added a negative voltage to the tungsten wire and added a positive voltage to the gold particles. Unexpectedly, a signal, which was opposite to the signal at the input, appeared at the output. The result of the preliminary test was that the voltage magnification was 2 and the upper limit frequency was up to 10 kHz. This means that it was unnecessary to make an oxide film on the surface of the germanium crystal. The gold particle can be directly contacted with the germanium crystal surface to obtain a good response frequency.

Bardeen keenly realized that a new physical phenomenon different from the addition of electrolyte occurred at the interface between the gold particles and the germanium crystal. According to this finding, he redesigned a set of experiment. The key of experiment is to make the tungsten wire contact on the surface of germanium crystal close to the metal electrode as far as possible. After the calculation, Bardeen pointed out that the distance should be up to 50μm. Brattain and technicians quickly made a set of experimental devices which met the requirement of Bardeen. On 16th December, they conducted the first experiment after the improvement and obtained 1.3 times the output power gain and 15 times the output voltage gain. Therefore, some scholars suggest that this day should be determined as the invention day of the transistor. 

On 23rd December, the semiconductor research team led by Shockley used the solid amplifier to conduct the experiment of amplifying the audio for the supervisors of Bell Labs. This was an audio amplification experiment without using an electron tube and succeeded as expected. Later, research team named the solid amplifier “transistor”. The transistor is called double point contact transistor because the transistor is formed by the contact between two wires and semiconductor.

Patent agent of Bell Labs finished the patent filing of point-contact transistor on 17th June. On June 23, Bell showed their transistor device to U.S. military representatives and was finally allowed to make it public. Meanwhile, Shockley and Pearson, Bardeen and Brattain collaborated to write a series of essays on transistors and the operation principle for Physical Review. After all the preparations were made, Bell held a press conference in the headquarters building on June 30 to unveil the world's first transistor. 

Since then, the single spark of transistor set by Bardeen and Brattain in 1947 started a prairie fire. At present, two-dimensional materials such as tungsten disulfide and tungsten diselenide, which have excellent properties such as electricity, optics, plasma, electrochemistry and electrocatalysis, have become the new favorite of the next generation of computer transistor study.