Paper TF-TuM1
Fabrication of Top Gate Graphene Transistor using Physically Transferrable High-k Nanosheet using Atomic Layer Deposition

Tuesday, October 29, 2013, 8:00 am, Room 104 A

Graphene, a single layer of hexagonal carbon atom structure with very high mobility (more than 200,000 cm²/Vs at 4.2 K for suspended) draws great attention as a promising material for future nanoelectronics and finally a substitution of silicon. To fabricate devices, especially transistors, gate dielectric is an essential component, which can significantly impact the device performance. Exploring graphene for future devices requires deposition of dielectric materials on graphene. However, deposition of high-κ dielectrics directly onto graphene is difficult task due to the nucleation problem preventing the formation of high quality oxide on graphene because of chemical inertness of graphene surface. Previous reports to deposit high-κ dielectrics on graphene have resulted in significant degradation in electrical properties of graphene. Here, we describe a new strategy to integrate graphene with high quality high-k dielectrics by transferring high-k dielectric nanosheet onto graphene. To fabricate a high-k dielectric nanosheet, we firstly prepared spin-coated water-soluble poly(acrylic acid) (PAA) on Si substrate as a sacrificial layer and high-k dielectric thin film was deposited on the sacrificial layer using atomic layer deposition (ALD) process. The high-k dielectric nanosheet was fabricated by soaking the sample in water and removing the sacrificial layer. Dielectric properties of high-k nanosheet show similar dielectric constant with ALD thin film and lower hysteresis (~ 0 mV) and interface state density (1.7 x 10¹¹ cm^-2eV^-1) than thin film (~ 200 mV, 7.6 x 10¹¹ cm^-2eV^-1). We fabricated and characterized top gate graphene transistors using both directly deposited high-k thin film on graphene using ALD and high-k dielectric nanosheet as gate dielectrics. Fabricated graphene device using ALD on graphene did not operate properly. Using high-k nanosheet as the gate dielectrics, we have demonstrated top gate graphene transistors with field-effect mobility up to 2,000 cm²/Vs and ~ 0 V of Dirac voltage. This method opens a new way to high-performance graphene devices to impact broadly from high frequency high speed circuits to flexible electronics.