TY - CHAP A1 - Langer, Christoph A1 - Ławrowski, Robert Damian A1 - Prommesberger, Christian A1 - Dams, Florian A1 - Serbun, Pavel A1 - Bachmann, Michael A1 - Müller, Günter A1 - Schreiner, Rupert T1 - High aspect ratio silicon tip cathodes for application in field emission electron sources T2 - 2014 27th International Vacuum Nanoelectronics Conference (IVNC), 6-10 July 2014, Engelberg, Switzerland N2 - Precisely aligned arrays of sharp tip structures on top of elongated pillars were realized by using an improved fabrication process including an additional inductively-coupled-plasma reactive-ion etching step. Arrays of n-type and p-type silicon with 271 tips have been fabricated and investigated. Those structures have a total height of 5–6 µm and apex radii less than 20nm. Integral field emission measurements of the arrays yielded low onset-fields in the range of 8–12V=µm and field enhancement factors between 300 and 700. The I-E curves of n-type structures showed the usual Fowler-Nordheim behaviour, whereas p-type structures revealed a significant saturation region due to the limited number of electrons in the conduction band and a further carrier depletion effect caused by the pillar. The maximum integral current in the saturation region was 150 nA at fields above 30V=µm. An excellent stability of the emission current of less than ± 2% fluctuation was observed in the saturation region. For n-type Si a maximum integral current of 10 µA at 24V=µm and an average current stability with a fluctuation of ± 50% were measured. KW - Current measurement KW - Etching KW - FABRICATION KW - field emission KW - field emitter array KW - GEOMETRY KW - Iron KW - Sensor arrays KW - silicon KW - silicon tip Y1 - 2014 U6 - https://doi.org/10.1109/IVNC.2014.6894824 SP - 222 EP - 223 PB - IEEE ER - TY - CHAP A1 - Ławrowski, Robert Damian A1 - Langer, Christoph A1 - Prommesberger, Christian A1 - Dams, Florian A1 - Bachmann, Michael A1 - Schreiner, Rupert T1 - Fabrication and simulation of silicon structures with high aspect ratio for field emission devices T2 - 2014 27th International Vacuum Nanoelectronics Conference (IVNC), 6-10 July 2014, Engelberg, Switzerland N2 - To obtain higher field enhancement factors of Si-tip structures, we present an improved fabrication process utilizing reactive-ion etching (RIE) with an inductively coupled plasma (ICP). In our design, a pillar under the tips is realized by a combination of RIE with ICP. With adjusted power settings (≈ 240 W) and step times (<; 5 s), vertical slopes with a low roughness of approximately 10 nm to 20 nm are possible. The remaining silicon is oxidized thermally to sharpen the emitters. A final tip radius of R <; 20 nm is obtained for the tips of the emitters. The pillar height HP can be mainly adjusted by the duration of the ICP-etching step. A total emitter height of H ≈ 6 μm with a pillar height of HP ≈ 5 μm is achieved. Simulations with COMSOL Multiphysics® are applied to calculate the field enhancement factor β. A two-dimensional model is used in rotational symmetry. In addition to the previous model, a pillar with a varying diameter ØP and height HP is added. A conventional emitter (H = 1 μm and R = 20 nm) placed on a pillar of the height HP ≈ 5 μm approximately results in a three times higher β-factor (β≈ 105). By decreasing the diameter ØP a slight increase of the β-factor is observed. However, the aspect ratio of the emitter mainly influences on the β-factor. KW - Anodes KW - CATHODES KW - FABRICATION KW - field emission KW - field emitter array KW - field enhancement factor KW - Iterative closest point algorithm KW - Lead KW - silicon tips Y1 - 2014 U6 - https://doi.org/10.1109/IVNC.2014.6894805 SP - 193 EP - 194 PB - IEEE ER - TY - JOUR A1 - Schreiner, Rupert A1 - Langer, Christoph A1 - Prommesberger, Christian A1 - Dams, Florian T1 - Compact and Energy-Efficient Field Emission Cathodes for Sensor Applications JF - Advanced Materials Research N2 - We report on miniaturized silicon field emitter arrays for the application in compact and energy-saving vacuum-microelectronic devices, e.g. sensors or x-ray tubes. Since standard silicon semiconductor technology has been used for the fabrication, they may be easily integrated with other silicon based circuits and devices on the same chip. The silicon tip geometry and the operating conditions were optimized in order to obtain highly uniform and stable electron field emission from large area cathode arrays. A series of uniform hexagonal tip arrays containing each 547 tips were fabricated and characterized. The electron emission properties of both individual tips as well as of complete emitter arrays were investigated. A saturation level in the voltage-current characteristics was found, which can be explained by the limitation of the supply of electrons due to the p-type silicon wafer material. When operating the arrays in the current saturation regime at an emission current of ~ 1 nA per tip, a highly stable and low noise emission can be observed. KW - field emission KW - Si-Tip Cathodes KW - Vacuum Sensors Y1 - 2014 U6 - https://doi.org/10.4028/www.scientific.net/amr.1024.372 VL - 1024 SP - 372 EP - 375 PB - Scientific.net ER -