A multi-technique approach to understanding delithiation damage in LiCoO2 thin films

We report on the delithiation of LiCoO₂ thin films using oxalic acid (C₂H₂O₄) with the goal of understanding the structural degradation of an insertion oxide associated with Li chemical extraction. Using a multi-technique approach that includes synchrotron radiation X-ray diffraction, scanning electron microscopy, micro Raman spectroscopy, photoelectron spectroscopy and conductive atomic force microscopy we reveal the balance between selective Li extraction and structural damage. We identify three different delithiation regimes, related to surface processes, bulk delithiation and damage generation. We find that only a fraction of the grains is affected by the delithiation process, which may create local inhomogeneities. However, the bulk delithiation regime is effective to delithiate the LCO film. All experimental evidence collected indicates that the delithiation process in this regime mimics the behavior of LCO upon electrochemical delithiation. We discard the formation of Co oxalate during the chemical extraction process. In conclusion, the chemical route to Li extraction provides additional opportunities to investigate delithiation while avoiding the complications associated with electrolyte breakdown and simplifying in-situ measurements.

Pore collapse and regrowth in silicon electrodes for rechargeable batteries

In-operando Neutron Reflectometry establishes the pore collapse and regrowth (PCRG) mechanism in amorphous Si. Upon lithiation, porosity is first consumed by expansion of solid Si domains, with little thickness increase. After, the whole film expands. Porosity returns upon delithiation.

MOF-based electronic and opto-electronic devices

Emergent properties resulting from the ordered structure and synthetic versatility of nanoporous metal–organic frameworks offer exciting possibilities for electronic devices.

Field Emission Properties of Disordered and Partially Ordered Nano Clustered Carbon Films

The fabrication of an efficient cold cathode emitter from carbon is based on a combination of material properties, which must be carefully tailored during deposition. We present the electron emission characteristics of several carbon films deposited by cathodic arc evaporation, and their correlation with the chemical composition, microtexture and microstructure of the films. The emission threshold field voltage, emission site density, uniformity and stability of both tetrahedral amorphous carbon, nitrogen doped carbon and nanoclustered carbon films will be reviewed. We will also address issues related to the deposition method, such as substrate temperature, defect density and scalability, in connection with requirements for the fabrication of field emission displays.

Effect of critical dimension variation on SAW correlator energy

The effect of critical dimension (CD) variation and metallization ratio on the efficiency of energy conversion of a surface acoustic wave (SAW) correlator is examined. We find that a 10% variation in the width of finger electrodes predicts only a 1% decrease in the efficiency of energy conversion. Furthermore, our model predicts that a metallization ratio of 0.74 represents an optimum value for energy extraction from the SAW by the interdigitated transducer (IDT).

Silver growth on micropatterned DNA chips: effect of growth conditions and morphology on I-V behavior

An approach to the design of DNA-based electronics is presented, in which standard microfabrication processes are integrated with lithographic patterning of single-stranded oligonucleotides followed by hybridization to gold-labeled, complementary oligonucleotides and subsequent silver enhancement for signal amplification. The resulting bioinorganic devices demonstrate micron-sized geometric features, very little non-specific silver growth, a distinct silver morphology in the patterned region, and a 10(9)-fold increase in conductivity across an electrode gap when compared with control devices. This approach may prove useful for the fabrication of high fidelity, high-density arrays for DNA-based biosensing applications.