South Korean team makes transistor components by selectively replacing atoms
In short
Researchers at South Korea's Institute for Basic Science developed a method to form transistor components within a thin semiconductor film by selectively replacing atoms. The findings were published in Science, Korean outlets reported on October 16.
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Researchers at South Korea's Institute for Basic Science developed a way to make transistor components within a thin semiconductor film by selectively replacing its atoms, according to Korean reports published October 16. The institute's van der Waals quantum materials research team produced the semiconductor, insulating layer and contact region without separately stacking different materials. The findings appeared in Science. [ 1 , 2 , 3 ]
The method starts with tungsten diselenide, in which selenium layers surround a tungsten layer. Researchers kept the tungsten while selectively replacing selenium with oxygen, sulfur or tellurium. These substitutions produced insulating tungsten oxide, semiconducting tungsten disulfide and semimetallic tungsten ditelluride, respectively, Asia Economy and Newsis reported. [ 2 , 3 ]
The researchers used small gaps between layers as barriers to the movement of reacting atoms. By adjusting reaction temperature and gas pressure, they controlled conversion in layers about 0.7 nanometers thick. Semiconductor processing masks allowed them to select the locations to change within the film, according to Asia Economy and Newsis. [ 2 , 3 ]
Chosun Ilbo and Asia Economy reported that a tenfold change in current required a gate-voltage change of 61.3 millivolts, close to the roughly 60-millivolt theoretical minimum for conventional transistors at room temperature. The ratio between current in the on and off states exceeded 10 million. Asia Economy also reported a 35.5-millielectronvolt barrier for charge moving from metal electrodes into the semiconductor after the semimetal contact layer was added. [ 1 , 2 ]
Asia Economy reported that the team also stacked p-type and n-type transistors to demonstrate a complementary inverter operating at 1 volt. Chosun Ilbo said the researchers planned to expand the technique to semiconductor wafer size and study its application in three-dimensional integrated circuits. The reports describe the approach as a way to reduce difficulties in assembling ultrathin semiconductor devices. [ 1 , 2 , 3 ]
Why it matters
The method could simplify the assembly of two-dimensional transistors by creating different electrical properties within one film. The researchers plan to scale it to wafer size and study applications in vertically stacked circuits.