Carbon Wonderland from an Engineering Perspective

The talk will introduce some of the application-driven topics in our group. Applications of graphenic carbon as x-ray transmission windows as well as in DRAM capacitors and diodes will be demonstrated. A novel x-ray transmission window based on graphenic carbon (GC) has been developed and integrated into a silicon drift detector (SDD) with much better performance than beryllium transmission windows that are currently used in the field. It is now used in products from Olympus, Bruker and Oxford. GC integrated on a silicon frame allows for a 7 mm wide window which does not use a mechanical support grid or additional light blocking layers. Compared to beryllium, the novel GC window exhibits an improved x-ray transmission in the important low energy region (0.1 keV - 3 keV) enabling the detection of elements down to carbon while demonstrating excellent mechanical stability, as well as light and vacuum tightness. Be-windows with an opening diameter of 7 mm are specified to withstand a differential pressure of 2 bar. The GC window with a thickness of 1 micrometer exceed this requirement by far. Pressure cycle fatigue for Be-windows is specified to ∼ 20k cycles, while GC has already demonstrated more than 10 million pressure cycles without damage. Therefore, the newly established GC window, can replace beryllium in x-ray transmission windows with a nontoxic and abundant material. Contact resistance and thermal degradation of metal-silicon contacts are challenges in nanoscale CMOS as well as in power device applications. Titanium silicide (TiSi) contacts are commonly used metal-silicon contacts, but are known to diffuse into the active region under high current stress. We show that a graphenic carbon (C) contact to n-type silicon (C-Si) has the same low Schottky barrier height of 0.45 eV as TiSi, but a much improved reliability against high current stress. The C-Si contact is over 100 million times more stable against high current stress pulses than the conventionally used TiSi junction. The C-Si contact properties even show promise to establish an ultra-low, high temperature stable contact resistance. The finding has important consequences for the enhancement of reliability in power devices as well as in Schottky-diodes and electrical contacts to silicon and semiconductors in general (IEDM 2016, IEDM 2018).     «

The talk will introduce some of the application-driven topics in our group. Applications of graphenic carbon as x-ray transmission windows as well as in DRAM capacitors and diodes will be demonstrated. A novel x-ray transmission window based on graphenic carbon (GC) has been developed and integrated into a silicon drift detector (SDD) with much better performance than beryllium transmission windows that are currently used in the field. It is now used in products from Olympus, Bruker and Oxford....     »