Germanium‐Based Nanomaterials for Rechargeable Batteries

Germanium‐based nanomaterials have emerged as important candidates for next‐generation energy‐storage devices owing to their unique chemical and physical properties. In this Review, we provide a review of the current state‐of‐the‐art in germanium‐based materials design, synthesis, processing, and application in battery technology. The most recent advances in the area of Ge‐based nanocomposite electrode materials and electrolytes for solid‐state batteries are summarized. The limitations of Ge‐based materials for energy‐storage applications are discussed, and potential research directions are also presented with an emphasis on commercial products and theoretical investigations.     

A Germylene Stabilized by Homoconjugation

The synthesis of a bicyclic germylene from the reaction of a germole dianion with hafnocene dichloride is reported. This germylene is stabilized by a homoconjugative interaction of the dicoordinated germanium atom with a remote C=C double bond. First reactivity studies revealed its nucleophilic character and resulted in the synthesis of bimetallic hafnium/iron and hafnium/tungsten complexes with a germylene group linker.     

Structures,Oxidation, and Charge Transport of Phosphorus‐Doped Germanium Nanocrystals

The doping of semiconductor nanocrystals (NCs) is crucial for the optimization of the performance of devices based on them. In contrast to recent progress on the doping of compound semiconductor NCs and silicon NCs, the doping of germanium (Ge) NCs has lagged behind. Here it is shown that Ge NCs can be doped with phosphorus (P) during synthesis by a nonthermal plasma. It is found that there are more P atoms in the NC near‐surface region than in the NC core. P doping modifies the surface state of Ge NCs. Compressive strain can be incuced in Ge NCs by P which can explain the P‐doping‐enhanced oxidation resistance of Ge NCs. Stable dispersions of P‐doped Ge NCs in acetonitrile can be cast to produce films for field‐effect transistors (FETs). FET analysis shows that the electrical conductivity and electron mobility of a Ge‐NC film increase with the increase of the P doping level, although the electrical activation efficiency of P in the Ge‐NC film is low. Finally, atomic layer deposition of aluminum oxide at the surface of P‐doped Ge NCs is shown to improve the performance of the FETs.     

离子色谱法快速连续测定锗和锡的研究

介绍了一种快速测定锗和锡的新方法──离子色谱法。锗和锡在双功能的分离柱上被分离后进行柱后显色反应,然后经可见检测器于５２０ｎｍ处检测。此法具有较高的灵敏度和选择性,整个分析过程仅需５ｍｉｎ,样品分析结果令人满意。     

Axial macrosegregation in Ga‐doped germanium grown by the vertical gradient freeze technique with a rotating magnetic field

The impact of a rotating magnetic field (RMF) on the axial segregation in Vertical Gradient Freeze (VGF) grown, Ga doped germanium is investigated. Growth experiments were performed using the VGF‐RMF as well as the conventional VGF technique. Carrier concentration profiles characterising the Ga segregation were measured by the Spreading Resistance method and calibrated using Hall values of carrier concentration and mobility. The Ga concentration rises more gradually under RMF action, i.e., the dopant segregation is significantly reduced by the rotating field. This effect is attributed to a better mixing of the melt. Numerical results on the flow velocity confirm this explanation. The RMF induced flow is much more intense than the natural buoyant convection due to the radial temperature gradient and leads to a pronounced decrease of the effective partition coefficient k_eff. In the early stages of growth a k_eff value close to k₀ was obtained, i.e., the gallium was almost homogeneously distributed within the melt. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Local Vibrations of Oxygen-Containing Thermal Donors in Germanium

The vibrational absorption bands associated with some types of double thermal donors (TD) in Ge enriched with the oxygen isotopes ¹⁶O and ¹⁸O have been identified. The thermal donors were formed during heat treatment of Ge:O crystals at 300 and 350°C. Absorption spectra were measured at room temperature and at 10 K. The formation of the thermal donors was accompanied by the appearance of three absorption bands, which in the Ge:¹⁶O spectra at room temperature are located at 600, 740, and 780 cm^–1. In low-temperature measurements, the bands at 600 and 780 cm^–1 exhibited splitting into series of narrow lines (up to 9) associated with some types of thermal donors (TD1–TD9). The absorption spectra measured at 10 K after different cooling conditions display bistability of the first four types of thermal donors (TD1–TD4). In the samples cooled by illumination with light in the region of frequencies of the fundamental absorption of Ge, pairs of lines are observed that belong to the bistable thermal donors in the helium-like configuration of double donors (DD). After cooling the samples in the dark, these pairs of lines are replaced by three new bands, which belong to local vibrational modes of bistable thermal donors in the low-energy neutral configuration. Based on the isotopic shift of the local vibrational modes of the thermal donors in Ge:¹⁶O and Ge:¹⁸O, a rigorous proof of the oxygen atoms entering into the composition of thermal donors is obtained.