1. Spectroscopy of Hybrid Inorganic/Organic Interfaces Transport Properties Dietrich RT Zahn

2. (vi) The Overall Device Performance GaAs(100) Organic Interlayer Metal V I (iv) The Interface between the Organic Molecules and the Metal (iii) The Organic Molecular Film (ii) The Interface between GaAs Substrate and Organic Molecules (i) The GaAs Substrate Surface (v) The Metal film

3. PTCDA modified Ag/GaAs(100) Schottky Contacts 30 nm PTCDA interlayer. Reverse bias/Low forward bias Increase in current (  1000) Decrease in barrier height ( -150 meV) High forward bias Deviation from pure thermionic emission. 3,4,9,10- P erylene t etra c arboxylic d i a nhydride ( C 24 H 8 O 6 ) Ag/PTCDA/GaAs Ag/GaAs

4. IV Characteristics of Ag/PTCDA/GaAs(100) Diodes Low injection region:  Current I increases with layer thickness d.  Current can be described by thermionic emission. High injection region:  Current I decreases with layer thickness d.  Space charge effects govern the transport behaviour.

5. I/V Characteristic of organic modified Schottky Contacts Thermionic emission Space charge limited current (SCLC) Series resistance Diode parameters n =1.28  0.01  B,eff =(0.66  0.01)eV R S =(6.8  1.0)   eff =(1.3  0.3)  10 -2 cm 2 /Vs (Mott-Gurney) V = V barrier + V org + V R 30 nm PTCDA SCLC in the PTCDA layer

6. Difference in barrier height: in agreement with PES results. St. Hohenecker et al., J. of Electron. Spectr. and Rel. Phen., 96 (1998) 97. due to an additional S- induced surface dipole. T.U. Kampen et al., Surf. Sci. 331-333 (1995) 490; W. Mönch, Europhys. Lett. 27 (1994) 479. Effect of Sulfur Treatments on Ag/GaAs(100) Schottky contacts Ag/GaAs(100) n=1.10  0.01  B,eff =(0.82  0.01)eV Ag/S-GaAs(100) n=1.09  0.01  B,eff =(0.59  0.01)eV

7. Low injection region: - Initial decrease in current, then increase - Saturation above 30 nm. High injection region: - Dominated by SCLC IV Characteristics for Ag/PTCDA/S-GaAs(100)

8. Ag/PTCDA/GaAs  B =0.64~0.81 eV Ag/PTCDA/S-GaAs  B = 0.54~0.73 eV Effective Barrier Height for Ag/PTCDA/GaAs(100) Diodes The effective barrier height can be tuned by different surface treatments and by the organic modification.

9. CV Characteristics Ag/PTCDA/GaAs(100) Diodes Frequency: 1MHz C O : Capacitance of PTCDA C D : Capacitance of GaAs  Unmodified contact C D  0.22 nF  60 nm PTCDA interlayer Capacity of the organic layer decreases: C = 0.134 nF  C O  0.34 nF GaAs space charge region is not changed! 3 nm 5 nm 10 nm 15 nm 30 nm 60 nm Ag/GaAs

10. IV Characteristics of Ag/PTCDA/GaAs(100) Diodes Low injection region:  Current I increases with layer thickness d.  Current can be described by thermionic emission. High injection region:  Current I decreases with layer thickness d.  Space charge effects govern the transport behaviour.

11. Low injection region: - Initial decrease in current, then increase - Saturation above 30 nm. High injection region: - Dominated by SCLC IV Characteristics for Ag/PTCDA/S-GaAs(100)

12. Ag/PTCDA/GaAs  B =0.64~0.81 eV Ag/PTCDA/S-GaAs  B = 0.54~0.73 eV Effective Barrier Height for Ag/PTCDA/GaAs(100) Diodes The effective barrier height can be tuned by different surface treatments and by the organic modification.

13. Assignment: B - GaAs bulk ET2 C - PTCDA D - PTCDA After air exposure  Dramatic increase of C, D  Increase of trap density The Influence of Air Exposure on Deep Level of Ag/PTCDA(100ML)/GaAs:S-2  1 Decrease of effective mobility in PTCDA layer Change the energy level at the interface