<p>Researchers, including one of Indian-origin, have developed the smallest transistor reported to date, breaking a major size barrier with a gate only one nanometre long.<br /><br />For more than a decade, engineers have been eyeing to shrink the size of components in integrated circuits. The laws of physics had set a 5-nanometre threshold on the size of transistor gates among conventional semiconductors, about one-quarter the size of high-end 20-nanometre-gate transistors now on the market.<br /><br />The research team led by Ali Javey from Lawrence Berkeley National Laboratory (Berkeley Lab) in the US created the new transistor with a working one-nanometre gate. For comparison, a strand of human hair is about 50,000 nanometres thick.<br /><br />"We made the smallest transistor reported to date. The gate length is considered a defining dimension of the transistor," said Javey.<br /><br />"We demonstrated a 1-nanometre-gate transistor, showing that with the choice of proper materials, there is a lot more room to shrink our electronics," he said.<br /><br />The key was to use carbon nanotubes and molybdenum disulfide (MoS2), an engine lubricant commonly sold in auto parts shops.<br /><br />"The semiconductor industry has long assumed that any gate below 5 nanometres wouldn't work, so anything below that was not even considered," said study lead author Sujay Desai, a graduate student in Javey's lab.<br /><br />"By changing the material from silicon to MoS2, we can make a transistor with a gate that is just one nanometre in length, and operate it like a switch," said Desai.<br /><br />Transistors consist of three terminals: a source, a drain, and a gate. Current flows from the source to the drain, and that flow is controlled by the gate, which switches on and off <br />in response to the voltage applied.<br /><br />Both silicon and MoS2 have a crystalline lattice structure, but electrons flowing through silicon are lighter and encounter less resistance compared with MoS2. That is a boon when the gate is 5 nanometres or longer.<br /><br />However, below that length, a quantum mechanical phenomenon called tunnelling kicks in, and the gate barrier is no longer able to keep the electrons from barging through from the source to the drain terminals.<br /><br />"This means we can't turn off the transistors. The electrons are out of control," said Desai.<br /> Because electrons flowing through MoS2 are heavier, their flow can be controlled with smaller gate lengths.<br /><br />MoS2 can also be scaled down to atomically thin sheets, about 0.65 nanometres thick, with a lower dielectric constant, a measure reflecting the ability of a material to store energy in an electric field.<br /><br />These properties, in addition to mass of the electron, help improve the control of the flow of current inside the transistor when the gate length is reduced to one nanometre.<br />"This work demonstrated the shortest transistor ever," Javey added.</p>
<p>Researchers, including one of Indian-origin, have developed the smallest transistor reported to date, breaking a major size barrier with a gate only one nanometre long.<br /><br />For more than a decade, engineers have been eyeing to shrink the size of components in integrated circuits. The laws of physics had set a 5-nanometre threshold on the size of transistor gates among conventional semiconductors, about one-quarter the size of high-end 20-nanometre-gate transistors now on the market.<br /><br />The research team led by Ali Javey from Lawrence Berkeley National Laboratory (Berkeley Lab) in the US created the new transistor with a working one-nanometre gate. For comparison, a strand of human hair is about 50,000 nanometres thick.<br /><br />"We made the smallest transistor reported to date. The gate length is considered a defining dimension of the transistor," said Javey.<br /><br />"We demonstrated a 1-nanometre-gate transistor, showing that with the choice of proper materials, there is a lot more room to shrink our electronics," he said.<br /><br />The key was to use carbon nanotubes and molybdenum disulfide (MoS2), an engine lubricant commonly sold in auto parts shops.<br /><br />"The semiconductor industry has long assumed that any gate below 5 nanometres wouldn't work, so anything below that was not even considered," said study lead author Sujay Desai, a graduate student in Javey's lab.<br /><br />"By changing the material from silicon to MoS2, we can make a transistor with a gate that is just one nanometre in length, and operate it like a switch," said Desai.<br /><br />Transistors consist of three terminals: a source, a drain, and a gate. Current flows from the source to the drain, and that flow is controlled by the gate, which switches on and off <br />in response to the voltage applied.<br /><br />Both silicon and MoS2 have a crystalline lattice structure, but electrons flowing through silicon are lighter and encounter less resistance compared with MoS2. That is a boon when the gate is 5 nanometres or longer.<br /><br />However, below that length, a quantum mechanical phenomenon called tunnelling kicks in, and the gate barrier is no longer able to keep the electrons from barging through from the source to the drain terminals.<br /><br />"This means we can't turn off the transistors. The electrons are out of control," said Desai.<br /> Because electrons flowing through MoS2 are heavier, their flow can be controlled with smaller gate lengths.<br /><br />MoS2 can also be scaled down to atomically thin sheets, about 0.65 nanometres thick, with a lower dielectric constant, a measure reflecting the ability of a material to store energy in an electric field.<br /><br />These properties, in addition to mass of the electron, help improve the control of the flow of current inside the transistor when the gate length is reduced to one nanometre.<br />"This work demonstrated the shortest transistor ever," Javey added.</p>