Final Report Summary - FLATRONICS (Electronic devices based on nanolayers)
One of the driving forces in the current research on 2D materials beyond graphene are advances in electronic devices based on dichalcogenides, where our group was the first to report a switchable field-effect transistor (FET) based on a 2D semiconductor, a monolayer of MoS2. FETs are the basic building block of digital electronic circuits where they are used as switches, capable of switching between the highly conductive ON state and highly insulating OFF state. The semiconductor industry is currently facing large problems in part because further miniaturization of FETs in circuits increases the current in the OFF state, resulting in increased power consumption. Using 2D materials such as MoS2 could be advantageous in this context as they would result in decreased power consumption due to their atomic scale thickness. Showing that transistors and electronic circuits could be implemented using a new family of materials is therefore the first step in them being seriously considered by the semiconductor industry.
We made this first step by building a field-effect transistor incorporating monolayer MoS2 as the channel material which displayed a room-temperature on/off ratio of 10^8 and negligible leakage currents. Transistors for digital applications need to have at least an on/off ratio 10^4 for desktop applications and over 10^6 for mobile applications. At that time, the use of MoS2 for electronic devices was not seriously considered. Our work has resulted in the inclusion of MoS2 in the 2011 ITRS roadmap as an emerging research material and gained widespread attention in the scientific community and media which is now increasing its effort in studying this class of materials.
We continued our work by demonstrating analogue amplifiers with gain >1. We also integrated graphene and MoS2 into heterostructures that function as flash memory. Here graphene plays the role of electrical contacts while MoS2 works as a semiconducting channel and is the first example of such a combination. This shows that graphene could be used as a high-quality contact to MoS2 and related 2D semiconductors which could be interesting for the fabrication of transparent and flexible electronic circuits.
We have also demonstrated an ultrasensitive monolayer MoS2 photodetector that takes full advantage of the direct band gap and high-quality electrical contacts. The photodetector has a photoresponsivity of 880 A/W, a factor of ~10^6 higher than in first graphene devices. Because of its atomic scale thickness, MoS2 also has a very low noise equivalent power (NEP) of 1.8x10^-15 W Hz^-1/2, which is more than an order of magnitude improvement over state-of-the-art commercial Si avalanche photodiodes, implying that MoS2 could be used for fabricating sensors for low-light imaging.
We made this first step by building a field-effect transistor incorporating monolayer MoS2 as the channel material which displayed a room-temperature on/off ratio of 10^8 and negligible leakage currents. Transistors for digital applications need to have at least an on/off ratio 10^4 for desktop applications and over 10^6 for mobile applications. At that time, the use of MoS2 for electronic devices was not seriously considered. Our work has resulted in the inclusion of MoS2 in the 2011 ITRS roadmap as an emerging research material and gained widespread attention in the scientific community and media which is now increasing its effort in studying this class of materials.
We continued our work by demonstrating analogue amplifiers with gain >1. We also integrated graphene and MoS2 into heterostructures that function as flash memory. Here graphene plays the role of electrical contacts while MoS2 works as a semiconducting channel and is the first example of such a combination. This shows that graphene could be used as a high-quality contact to MoS2 and related 2D semiconductors which could be interesting for the fabrication of transparent and flexible electronic circuits.
We have also demonstrated an ultrasensitive monolayer MoS2 photodetector that takes full advantage of the direct band gap and high-quality electrical contacts. The photodetector has a photoresponsivity of 880 A/W, a factor of ~10^6 higher than in first graphene devices. Because of its atomic scale thickness, MoS2 also has a very low noise equivalent power (NEP) of 1.8x10^-15 W Hz^-1/2, which is more than an order of magnitude improvement over state-of-the-art commercial Si avalanche photodiodes, implying that MoS2 could be used for fabricating sensors for low-light imaging.