Step-conformal deposition of TiO2 and MnO2 electrodes on advanced silicon microstructures for 3D Li-ion microbatteries and micro-supercapacitors

Symposium C - Solid state ionics: thin films for energy and information applicationsTo get autonomous smart microsystem, a miniaturized power source should be integrated. As the device is surface limited, the energy and power performances of commercially available planar microbatteries and micro-supercapacitors are not sufficient to reach this goal. To improve their performances while keeping constant the footprint area of such devices, a 3D topology is proposed. The silicon micropillars and microtubes fabricated by a top down approach allows to reach a high area enlargement factor (AEF). Energy density can be increased by one or two orders of magnitude compared to standard planar micro-devices, thus providing improved autonomy to the powered microsytems. Step conformal deposition of platinum (current collector) and TiO2 (negative electrode of the Li-ion microbattery) are performed on the 3D structures by Atomic Layer Deposition facility. With a 3D scaffold having an AEF close to 25 combined with a 150 nm thick TiO2, a surface capacity of 0.2 mAh/cm2 at C/10 is reported. A micro-supercapacitor electrode based on a thin manganese dioxide film is conformably grown by pulsed electrodeposition on the 3D topologies. A MnO2 film (275 nm thick) reaches 250 mF/cm? at 5 mV/s. The surface capacitance is drastically enhanced compared to a standard 2D electrode with a comparable thickness. This study shows promising AEF leading to high energy density while keeping enough spacing in the microstuctrures array to allow the deposition of the overlying layers

Step conformal solid electrolyte deposited by ALD on robust 3D silicon scaffold for on chip Li-ion microbattery

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Interface characterization at nanometer scale using very high frequency ultrasounds

International audienceThe main objective of this work is to study the solid-solid interfaces using a very high frequency (3GHz) ultrasonic method in order to deduce in a non-destructive way and quantitatively the quality contact at the interface, fundamental parameter in tribology. The very high frequencies allow prospecting the state of contact at the nanometer scale. The determination of the contact surface between two polished materials (Silicon-Silica) was carried out. From the measured echoes diagram, the reflection coefficient and the elasticity of the interface were extracted and compared to the ones determined by a numerical approach presented by Greenwood and Williamso

Performances of the negative tone resist AZnLOF 2020 for nanotechnology applications

We present electron-beam lithography results on an AznLOF2020 UV negative tone resist. This study aims to define electron-beam lithography parameters compatible with microelectromechanical systems/nanoelectromechanical systems fabrication. Usually, one of the properties of the resist material is improved to the detriment of another. Resist properties have been investigated to form small features and high-aspect ratio lines. It has been demonstrated that thickness, postbaking time, development time, and dose effects can be varied and adjusted to form smallest patterns reproducible. Various writing strategies making use of test patterns comprising different nominal feature size were also studied. Additionally, high resolution and dense pattern fabrication with high-aspect ratios are demonstrated. Fifty-nanometer-wide lines spaced out at 100-nm intervals were achieved in a 200-nm-thick resist, and high-aspect ratio 200-nm-wide lines spaced out at 400-nm intervals were realized in a 1-μm-thick resist

Micro-patterning of LiPON and lithium iron phosphate material deposited onto silicon nanopillars array for lithium ion solid state 3D micro-battery

The paper deals with the methodology used to form regular pattern of sputtered thin films LiPON/LiFePO4 material acting respectively as the solid electrolyte and the positive electrode of the lithium ion solid state 3D micro-battery. The micromachining of the silicon periodic nanopillars array (negative electrode of the micro-battery) is also reported. The proposed study clearly demonstrates a breakthrough technology in the field of lithium ion micro-battery as the ecologically friendly LiFePO4 material has never been evaluated as the positive electrode

Silicon-microtube scaffold decorated with anatase TiO2 as a negative electrode for a 3D litium-ion microbattery

An optimized scaffold based on silicon microtubes is designed to increase the surface capacity of 3D lithium-ion microbatteries. High-depth, mechanically robust microstructures are fabricated using microelectronic facilities. Conformal deposition of anatase TiO2 is achieved using atomic layer deposition, realizing the targeted improvement for microbatteries; a surface capacity of 0.2 mA h cm-2 at a charge rate of C/10 is obtained in standard liquid electrolyte. This work paves the way for the fabrication of solid-state 3D Li-ion microbatteries with an efficient 3D scaffold