Surface and interface study of contacts to carbon-based films
EMSL Project ID
10196
Abstract
The proposed research consists of two projects, each of which pertains to different materials for electronic applications. The first project is part of a Nanoscale Interdisciplinary Research Team (NIRT), funded by NSF, and is based on the development and characterization of well-defined nanostructured carbon films for electronics. The film growth is based on the controlled pyrolysis of self-organizing block copolymers containing polyacrylonitrile. The nanostructures of the carbon films are templated on the morphology of the block copolymer precursors and have a wide range of nanostructures (e.g., spheres, cylinders, and lamellae). The nanostructured carbon materials obtained through this effort are expected to find a wide range of applications in devices ranging from field emission and flat panel displays, to energy conversion (photovoltaic cells) and energy storage (supercapacitors) devices to sensors and actuators. The team will develop prototypes of some of these devices and will identify the nanostructures/properties most desirable for each of their classes. The second project is also an NSF project; it pertains to organic semiconducting thin films. In particular we are focusing on polythiophene, which is one of the most widely studied classes of (semi)conducting polymers. This polymer system was advanced by a major development at Carnegie Mellon: controlled synthesis of highly regioregular head-to-tail poly(3-alkylthiophenes) (rr-PTs. rr-PTs are receiving particular attention, since their regioregularity leads to improved polymer chain conformations and packing, facilitating high electrical conductivity in the doped state (hundreds of S cm-1 in comparison with few S cm-1 for regiorandom polymers). These materials offer a combination of attributes that make them well suited for chemically-sensitive field-effect-transisors (FET’s), organic light emitting diodes (OLED’s), and high-efficiency OPV’s. However, a number of issues seriously impede the realization of polythiophene-based devices.
The development of the potential devices from the materials in both projects relies on an understanding of how to fabricate ohmic and rectifying contacts to the films. We are currently developing process methods at Carnegie Mellon and measuring the electrical properties of the films/contacts. To understand how to control the contact characteristics, it will be important to understand the interfacial chemistry and physics (e.g., Schottky barrier heights). As such, we propose to employ photoemission techniques (e.g., Auger, XPS, and UPS) at PNNL to study the interfacial chemistry and physics of selected metal/carbon samples. Metals and compounds have been selected based on various properties, such as workfunctions, resistivities, and chemistries with the semiconductor films. Photoemission characterization will allow us to measure
barrier heights and to understand how the interfacial chemistry affects the electrical properties (e.g., the workfunction-barrier height relationships).
The PI has some prior experience with photoemission techniques and has discussed the proposed ideas with Don Baer and Suntharampillai Thevuthasan at PNNL. In addition, as a part of the Nanoscience course held at EMSL in May 2004, Pranita Kulkarni (graduate student) received a hands-on introduction to XPS. We believe that this prior experience will be particularly helpful in the initial stages of the research projects.
Project Details
Project type
Exploratory Research
Start Date
2004-10-01
End Date
2006-11-10
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Kulkarni PB, LA McCullough, T Kowalewski, LM Porter, MH Engelhard, and DR Baer. 2011. "Study of surface cleaning methods and pyrolysis temperature on Nano-Structured Carbon Films using X-ray Photoelectron Spectroscopy." PNNL-SA-81008, Pacific Northwest National Laboratory, Richland, WA.
P. Kulkarni, “Electrical and Optical Properties of Carbon Films,” Ph.D. dissertation, Carnegie Mellon University (2008).
Singh A, T Nelson, J Belot, T Young, NR Dhumal, T Kowalewski, RD McCullough, P Nachimuthu, S Thevuthasan, and LM Porter. 2011. "Effect of Self-Assembled Monolayers on Charge Injection and Transport in Poly(3-hexylthiophene) based Field-Effect Transistors at Different Length Scales." PNNL-SA-78076, Pacific Northwest National Laboratory, Richland, WA. [Unpublished]