Semiconductor Nanocrystal Engineering by Applying Thiol‐ and Solvent‐Coordinated Cation Exchange Kinetics

Thiol‐ and solvent‐coordinated cation exchange kinetics have been applied to engineer the composition and crystallinity of novel nanocrystals. The detailed thermodynamics and kinetics of the reactions were explored by NMR spectroscopy, time‐dependent photoluminescence (PL) characterizations and theoretical simulations. The fine structure of the colloidal semiconductor nanocrystals (CSNCs) was investigated by X‐ray absorption near‐edge structure (XANES) and extended X‐ray absorption fine structure (EXAFS). In this way, high‐quality p‐type Ag‐doped ZnS quantum dots (QDs) and Au@ZnS hetero‐nanocrystals with a cubic phase ZnS shell were synthesized successfully.The unprecedented dominant Ag⁺‐dopant‐induced fluorescence and p‐type conductivity in the zinc‐blende ZnS are reported.     

Ferromagnetism and Kondo insulator behavior in the disordered periodic Anderson model

The effect of binary alloy disorder on the ferromagnetic phases of f-electron materials is studied within the periodic Anderson model. We find that disorder in the conduction band can drastically enhance the Curie temperature T{c} due to an increase of the local f moment. The effect may be explained qualitatively and even quantitatively by a simple theoretical ansatz. The emergence of an alloy Kondo insulator at noninteger filling is also pointed out.     

Detection of quantum critical points by a probe qubit

Quantum phase transitions occur when the ground state of a quantum system undergoes a qualitative change when an external control parameter reaches a critical value. Here, we demonstrate a technique for studying quantum systems undergoing a phase transition by coupling the system to a probe qubit. It uses directly the increased sensibility of the quantum system to perturbations when it is close to a critical point. Using an NMR quantum simulator, we demonstrate this measurement technique for two different types of quantum phase transitions in an Ising spin chain.     

Base doping and dopant profile control of SiGe npn and pnp HBTs

Incorporation of high doping concentrations and the creation and maintaining of steep doping profiles during processing are key enabler for high level RF performance of heterojunction bipolar transistors (HBTs). In this paper, we discuss results of base doping and dopant profile control for npn and pnp SiGe HBTs fabricated within 0.25 μm BiCMOS technologies. High level of electrically active B and P doping concentrations (up to 10²⁰ cm⁻³) have been incorporated into SiGe. By adding C to SiGe steep doping profiles have been maintained due to the prevention of dopant diffusion during device processing. It is shown that broadening of P doping profiles caused by segregation could be reduced by lowering the deposition temperature for the SiGe cap. B and P atomic layer doping is shown to be suitable for the creation of steep and narrow doping profiles. This result is demonstrating the capability of the atomic layer processing approach for future devices with critical requirements of dopant dose and location control.     

Palladium‐Catalyzed Domino CH/NH Functionalization: An Efficient Approach to Nitrogen‐Bridged Heteroacenes

Palladium‐catalyzed domino C?H/N?H functionalization for the synthesis of novel nitrogen‐bridged thienoacenes and 10H‐benzo[4,5]thieno[3,2‐b]indole derivatives from dihaloarene is reported. This domino sequence consists of initial C?H functionalization of the benzo[b]thiophene moiety, followed by Buchwald–Hartwig coupling. This transformation is also useful for the synthesis of highly π‐extended compounds.     

Synthesis of Highly Functionalized N,N-Diarylamides by an Anodic C,N-Coupling Reaction

We report an innovative, sustainable and straightforward protocol for the synthesis of N,N-diarylamides equipped with nonprotected hydroxyl groups by using electrosynthesis. The concept allows the application of various substrates furnishing diarylamides with yields up to 57 % within a single and direct electrolytic protocol. The method is thereby easy to conduct in an undivided cell with constant current conditions offering a versatile and short-cut alternative to conventional pathways.