Electrical Characterization

Members

• Dr. Daniel Lehmann
• Dipl.-Ing. Axel Fechner
• Dipl. Phys. Franziska Lüttich

Former Members:

•  Dipl. Phys. Evelyn Breyer
   

Topics

• Fabrication and characterization of inorganic and organic as well as hybrid electrical devices (diodes, organic field-effect transistors (OFETs), organic solar cells)
• Determination of organic sub- and monolayer modifications of barrier heights in Schottky diodes
• Investigation on the influence of dopants and impurities on the behaviour of electrical devices
• Electric field profiling of OFETs during operation (KPFM)

Equipment

• Keithley and HP Source Measure Units for I/V and C/V Characterization in the pA range
• Deep Level Transient Spectroscopy (DLTS)
• Charge Transient Spectroscopy (QTS)
• Anfatec AFM for Kelvin Probe Force Microscopy (KPFM) / potentiometry
• ABET Solar Simulator Sun 2000 (AM 1.5)
• Vacuum Chamber for In Situ Characterization
• Oven up to 1600 °C

Examples

Figure 1 illustrates the principles of organic field-effect transistors. The device consists of 8 individual layers: 1 and 2: metallic back contact layers 3: highly doped silicon substrate 4: SiO2 insulator 5 and 6: pads for electrical contacting 7: organic thin film – active layer 8: gold top contact with 200 µm to 20 µm gap (actual channel)	Figure 2 shows the  wiring inside the vacuum chamber for the in situ characterisation.
An exemplary I-V output characteristic for a pentacene based OFET is given in Figure 3.	During operation of the given OFET, its inherent electric field can be mapped using KPFM. Figure 4 shows the electric field strength for the pentacene OFET at various gate-source voltages.

Publications

E. Breyer, D. Lehmann, D.R.T. Zahn
e-Journal of Surface Science and Nanotechnology, 10 (2012) 538
Molecular Orientation of Copper Phthalocyanine Molecules on Crystalline and Amorphous Silicon Substrates

F. Lüttich, D. Lehmann, F. Seidel, D.R.T. Zahn, H. Graaf, C. v. Borczyskowski
e-Journal of Surface Science and Nanotechnology, 10 (2012) 538
Morphological Characterization of Spray-Coated PCBM Thin Films
 
F. Lüttich, D. Lehmann, M. Friedrich, Z. Chen, A. Faccetti, C. v.Borczyskowski, D.R.T. Zahn, H. Graaf
Phys. stat. sol. (a), 209 (3) (2012) 585
Interface Properties of OFETs Based on an Air-Stable n-Channel Perylene Tetracarboxylic Diimide Semiconductor
 
I. Korodi, D. Lehmann, T. Tippo, M. Hietschold, D.R.T. Zahn
Phys. stat. sol. (c) 7 (2) (2010) 456
Characterisation of Organic Field-Effect Transistors Using Metal Phthalocyanines as Active Layers
 
F. Lüttich, D. Lehmann, H. Graaf, D.R.T. Zahn, C. von Borczyskowski
Phys. stat. sol. (c) 7 (2) (2010) 452
Kelvin-Probe Studies of n-Conductive Organic Field-Effect Transistors During Operation
 
M. Arnold, A. Fechner, D.R.T. Zahn
Phys. stat. sol. (c) 7 (2) (2010) 321
Charge Transient Spectroscopy Measurements of Metal-Oxide-Semiconductor