Non-destructive imaging of buried electronic interfaces using a decelerated scanning electron beam

Recent progress in nanotechnology enables the production of atomically abrupt interfaces in multilayered junctions, allowing to increase the number of transistors in a processor, as known as Moore’s law, for example. However, uniform electron transport has never been achieved across the entire interfacial area in junctions due to the existence of local defects, causing local heating and reduction in transport efficiency. To date, junction uniformity has been predominantly assessed by cross-sectional transmission electron microscopy, which requires slicing and milling processes with potentially introducing additional damage and deformation. It is therefore essential to develop an alternative non-destructive method. Here we show a non-destructive technique using scanning electron microscopy to map buried junction properties. By controlling the electron-beam energy, we demonstrate the contrast imaging of local junction resistances at a controlled depth. This technique can be applied to any buried junctions, from conventional semiconductor and metal devices to organic devices

DESIGN AND OPTIMIZATION OF DIRECTLY HEATED LaB6 CATHODE ASSEMBLIES FOR ELECTRON-BEAM INSTRUMENTS.

A description is given of the design and testing of a directly heated, stable, electron source utilizing a single-crystal lanthanum hexaboride (LaB//6) cathode. The emitter mounting fixture consists of an adjustable molybdenum base unit supported on gas-impervious alumina or machinable glass. Single-crystal cathode rods are securely clamped and positioned between vitreous carbon jaws that are resistively heated. The complete assembly is designed to be a direct ″plug-in″ substitute for the conventional tungsten thermionic filaments used in electron-beam instruments. The cathode current density for LT AN BR 110 greater than axial orientations is found to be ten times higher than that for LT AN BR 100 greater than orientations under equivalent conditions, a value of 50 A cm** minus **2 being measured at 1500 degree C with an observed lifetime in excess of 300 h. Optimum vacuum conditions for high lifetime and stable operation are in the range 1 multiplied by 10** minus **6 Torr and lower. Comparison values for the emission at various temperatures from other borides, and tungsten, are also given

DESIGN AND OPTIMIZATION OF DIRECTLY HEATED LaB6 CATHODE ASSEMBLIES FOR ELECTRON-BEAM INSTRUMENTS.

A description is given of the design and testing of a directly heated, stable, electron source utilizing a single-crystal lanthanum hexaboride (LaB//6) cathode. The emitter mounting fixture consists of an adjustable molybdenum base unit supported on gas-impervious alumina or machinable glass. Single-crystal cathode rods are securely clamped and positioned between vitreous carbon jaws that are resistively heated. The complete assembly is designed to be a direct ″plug-in″ substitute for the conventional tungsten thermionic filaments used in electron-beam instruments. The cathode current density for LT AN BR 110 greater than axial orientations is found to be ten times higher than that for LT AN BR 100 greater than orientations under equivalent conditions, a value of 50 A cm** minus **2 being measured at 1500 degree C with an observed lifetime in excess of 300 h. Optimum vacuum conditions for high lifetime and stable operation are in the range 1 multiplied by 10** minus **6 Torr and lower. Comparison values for the emission at various temperatures from other borides, and tungsten, are also given

Anisotropy of thermionic electron emission values for LaB6 single-crystal emitter cathodes

Measurement of thermionic electron emission values for pointed LaB single-crystal emitter cathodes has shown that 〈110〉 axial orientations yield emission values ten times higher than 〈100〉 orientations at 1545°K. Minimum values were obtained for the 〈510〉 directions. These findings seem encouraging in achieving perhaps two orders of magnitude higher emission fluxes as compared to tungsten emitters.

Fabrication of ‘finger-geometry’ silicon solar cells by electrochemical anodisation

Cells made from crystalline silicon dominate the market for photovoltaics, but improvements in cost-effectiveness are still necessary for uptake to increase. In this paper, we investigate the fabrication of a cell structure which has the potential to be compatible with cheap low-purity silicon substrates. In our cell design the charge-collecting p–n junction protrudes into the substrate like fingers, thus significantly reducing the required carrier diffusion length compared to a front planar junction cell. The macroporous structure is created by electrochemical anodisation of an n-type silicon substrate in an HF and H2O2 (aqueous) electrolyte. The pores are loaded with a boron-containing glass which is then annealed to diffuse the dopant into the silicon substrate forming a volume junction. The anodisation conditions have been optimised using intentionally contaminated single-crystal silicon as a model system. We characterise the junction formed by electron beam induced current and current–voltage measurements. The anodisation study is extended to n-type multicrystalline silicon and it is found that the orientation of the grains strongly influences the geometry of the pores formed. The potential for using this cell structure for low-cost photovoltaics is discussed and potential problems are highlighted