Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Department

Electrical Engineering

First Advisor's Name

Dr. Irene Calizo

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Dr. Shekhar Bhansali

Second Advisor's Committee Title

Co-Committee Chair

Third Advisor's Name

Dr. Sakhrat Khizroev

Third Advisor's Committee Title

committee member

Fourth Advisor's Name

Dr. Nezih Pala

Fourth Advisor's Committee Title

committee member

Fifth Advisor's Name

Dr. Peggy Chunlei Wang

Fifth Advisor's Committee Title

committee member

Sixth Advisor's Name

Dr. Iftekhar Chowdhury

Sixth Advisor's Committee Title

committee member

Keywords

2D materials, Graphene, Germanene, Gas Sensor, MoS2, ZnO

Date of Defense

7-5-2017

Abstract

Two-Dimensional (2D) materials often exhibit distinguished properties as compared to their 3D counterparts and offer great potential to advance technology. However, even graphene, the first synthesized 2D material, still faces several challenges, despite its high mobility and high thermal conductivity. Similarly, germanene and silicene face challenges due to readily available semiconducting properties to be used in electronics, photonics or photocatalysis applications. Here, we propose two approaches to tune the band gap: One is by forming nanoribbon and edge functionalization and another by doping using inorganic nanoparticle’s interaction with 2D nanomaterials.

Edge functionalization of armchair germanene nanoribbons (AGeNRs) has the potential to achieve a range of band gaps. The edge atoms of AGeNRs are passivated with hydrogen (-H and -2H) or halogen (-F, -Cl,-OH, -2F,-2Cl) atoms. Using density functional theory calculations, we found that edge-functionalized AGeNRs had band gaps as small as 0.012 eV when functionalized by -2H and as high as 0.84 eV with -2F.

Doping can change the semiconducting behavior of AGeNRs to metal due to the half-filled band making it useful for negative differential resistance (NDR) devices. In the case of zigzag germanene nanoribbons (ZGeNRs), single N or B doping transformed them from anti-ferromagnetic (AFM) semiconducting to ferromagnetic (FM) semiconductor or half-metal. Lastly, formation and edge free energy studies revealed the feasibility of chemical synthetization of edge-functionalized and doped germanene.

Electronic, optical and transport properties of the graphene/ZnO heterostructure have been explored using first-principles density functional theory. The results show that Zn12O12 can open a band gap of 14.5 meV in graphene, increase its optical absorption by 1.67 times, covering the visible spectrum and extended to the infra-red (IR) range, and create slight nonlinear I-V characteristics depending on the applied bias. This agrees well with collaborative experimental measurement of a similar system.

In conclusion, we have successfully studied the potential use of edge functionalization, band gap periodicity in nanoribbon width, and doping in germanene nanoribbons. Structural stability was also studied to investigate the feasibility for experimental synthesization. Inorganic nanoparticle’s interaction with graphene envisages the possibility of fabricating photo-electronic device covering visible spectrum and beyond. Finally, graphene complexes were merged with naturally available direct band gap of monolayer MoS2 to build efficient energy harvesting and photo detecting devices.

Identifier

FIDC001977

ORCID

orcid.org/0000-0001-6186-6690

Share

COinS
 

Rights Statement

Rights Statement

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/
This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).