Two-dimensional BN buffer for plasma enhanced atomic layer deposition of Al2O3 gate dielectrics on graphene field effect transistors

Abstract

Here, we investigate the use of few-layer metal organic chemical vapor deposition (MOCVD) grown BN as a two-dimensional buffer layer for plasma enhanced atomic layer deposition (PE-ALD) of Al2O3 on graphene for top gated field effect transistors (FETs). The reactive nature of PE-ALD enables deposition of thin (2 nm) dielectrics directly on graphene and other two-dimensional materials without the need for a seed or functionalization layer; however, this also leads to significant oxidation of the graphene layer as observed by Raman. In FETs, we find this oxidation destroys conductivity in the graphene channel. By transferring thin (1.6 nm) MOCVD BN layers on top of graphene channels prior to PE-ALD, the graphene is protected from oxidation enabling BN/Al2O3 layers as thin as 4 nm. Raman and X-ray photoelectron spectroscopy on BN films show no significant oxidation caused by PE-ALD of Al2O3. Inserting the BN layer creates an atomically abrupt interface significantly reducing interface charges between the graphene and Al2O3 as compared to use of a 2 nm Al buffer layer. This results in a much smaller Dirac voltage (− 1 V) and hysteresis (0.9 V) when compared to FETs with the Al layer (VDirac = − 6.1 V and hysteresis = 2.9 V).

Plasma‐Enhanced Atomic Layer Deposition of Al2O3 on Graphene Using Monolayer hBN as Interfacial Layer

“…These works demonstrate an increased interest in being able to protect graphene from plasma damage. [33] In this work we demonstrate that even a monolayer of hBN on-top of graphene can act as an effective protective and interfacial layer for the graphene when PEALD with a very short plasma duration is used, enabling PEALD deposition of high quality and 10 nm thin Al2O3. Similar to graphene, hBN also has no dangling bonds, which can prevent proper nucleation in a thermal ALD process.…”

“…[ 33 ] Recently, thin films of hBN (1.6 nm) have been used as a protective buffer layer to protect graphene from damage during PEALD of Al 2 O 3 . [ 34 ] For very thin dielectrics, where the higher quality of dielectrics deposited by PEALD becomes important, a 1.6 nm buffer layer may be too thick and despite the thickness of the hBN there was still some damage to the graphene. These works demonstrate an increased interest in being able to protect graphene from plasma damage.…”

“…These works demonstrate an increased interest in being able to protect graphene from plasma damage. [ 34 ]…”

Spalling‐Induced Liftoff and Transfer of Electronic Films Using a van der Waals Release Layer

“…The BN layer itself can be transferred to function as an insulating or passivating layer. [ 40–41 ] Figure a shows a sp 2 ‐bonded BN film transferred to a SiO 2 /Si substrate, with the Raman spectrum confirming the transfer of the BN. MOCVD‐grown AlN and Ga 2 O 3 films were also transferred to a SiO 2 /Si substrate, as shown in Figure 4b,c.…”

Application of Adaptive PID Temperature Control Algorithm under Spatial Thermal Model of ALD Reaction Chamber

“…The combination of the control system and the vacuum pump provides power for the whole system. The reaction completes if the liquid in the precursor gasifies and enters the vacuum reaction chamber [13]. After each ALD reaction, the chemicals generated are rinsed with N2 to remove the determinations, and finally, a complete deposited film is formed [14].…”