Task:

• Growth and “quasi in-situ” characterization of photovoltaic materials using relevant vacuum based preparation methods
• Characterization of electronic properties of energy materials at the surface/interface on mm to nm scale
• Growth and study of layers and layer stacks towards complete devices

Specific information on the method:

• Growth by Plasma Enhanced Chemical Vapor Deposition – PECVD, Hot Wire Chemical Vapor Deposition – HWCVD), Sputter deposition, Atomic Layer Deposition – ALD
• Characterization by Photo electron spectroscopy: XPS/UPS, Total Yield Photoelectron Spectroscopy, Low Energy Electron microscopy: LEEM/PEEM, Scanning Probe Methods: AFM/STM/KPFM, TERS (under development)

Specific information on the equipment/instrumentation:

The system consists of 2 clusters for deposition and analysis linked by a sample transfer/separation system a magazine and 2 load locks. All transfer of samples is done by robots. The deposition cluster has a base pressure in the 10E-8 mbar range and the transfer/separation section and the analytic a handler in the 10E-9 mbar range. The analytical instruments operate typically at pressures of better than 10E-10 mbar. Samples/substrates can be loaded under normal laboratory conditions or using a vacuum box system.

Samples/limitations:

Suitable for solids or powders, conductive samples as well as insulators, biological samples
Limitation: sample stable under UHV conditions, maximum size 50 mm, radiation damage at high magnifications.

Samples/limitations:

For deposition samples/substrates are transferred using a carrier system which allows a size up to 10×10 cm². Smaller samples can be used with individual adapter systems. For the analytical system the sample size is limited to 2×2 cm² with strong demand on the precision of size and shape and polished sides are required.
For all samples, the thickness has to be between 0.3 and 1.1 mm.

Examples of typical analytical questions:

• Influence of the deposition parameters on the structure, the chemical composition and the electronic properties on a nanoscale
• Effect of the structure and the chemical composition of a layer on the energy levels and density of states
• Determination and design of the energy levels of semiconductor hetero-junction for optimum performance of the solar cells

Fields of research:

photovoltaics