We report on Bi 2 Sr 2 CaCu 2 O 8 (BSCCO) intrinsic Josephson junction stacks with improved cooling, allowing for a remarkable increase in emission frequency compared to the previous designs. We started with a BSCCO stack embedded between two gold layers. When mounted in the standard way to a single substrate, the stack emits in the range of 0.43-0.82 THz. We then glued a second, thermally anchored substrate onto the sample surface. The maximum voltage of this better cooled and dimension-unchanged sample was increased and, accordingly, both the emission frequencies and the tunable frequency range were significantly increased up to 1.05 THz and to 0.71 THz, respectively. This double sided cooling may also be useful for other "hot" devices, e.g., quantum cascade lasers. V C 2014 AIP Publishing LLC. [http://dx.

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Aqueous Zn-organic batteries have received considerable attention owing to their green, low-cost and high safe nature. Unfortunately, organic materials generally exhibit insulator nature ( � 10 À 10 S cm À 1 ), and most of reported promising performances of Zn-organic batteries are achieved with a low mass-loading ( � 2 mg cm À 2 ) in cathode, which is far away from practical application (10 mg cm À 2 ). Herein, we demonstrate a semi-conductive polymer poly(1,8diaminonaphthalene) (PDAN) cathode material for Zn batteries, which shows a moderate electronic conductivity (5.9 × 10 À 5 S cm À 1 ). Theoretical calculations and in situ/ex situ analysis reveal that the cathode involves a bipolar-type charge storage mechanism. Accordingly, the Zn//PDAN cell exhibits a promising capacity (140 mAh g À 1 at 0.1 A g À 1 ) and a remarkable cycle stability (1000 cycles without capacity fading) at a high mass-loading (10 mg cm À 2 ). These encouraging results shed light on the design of advanced organic electrode.

We report on the electrothermal behavior and the terahertz emission properties of a stand-alone Bi2Sr2CaCu2O8 intrinsic Josephson junction stack contacted in a three-terminal configuration. One terminal is used as a collective ground while the other two, contacting the stack from its right and left side, allow to vary the current injection profile. At high bias, a hot spot forms in the stack. Its appearance and position can be controlled by varying the ratios of the injected currents. Depending on this ratio, the emitted power can vary by an order of magnitude. Further, for a given total injection current, the device allows to vary the emission frequency on a 10% level by altering the injection profile. The overall tunability of the emission frequency, varying also the total bias current, is on the order of 20%.

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We report on a liquid-nitrogen-cooled compact source for continuous terahertz (THz) emission. The emitter is a Bi 2 Sr 2 CaCu 2 O 8þδ intrinsic Josephson-junction stack embedded between two gold layers and sandwiched between two MgO substrates. The radiation is emitted to free space through a hollow metallic tube acting as a waveguide. The maximum emission power is 1.17 μW. The tunable emission frequency bandwidth is up to 100 GHz with a maximum emission power at 0.311 THz. Since the operation voltage is about 1 V and the current is less than 30 mA, we are able to drive this terahertz source at 77 K with only one commercial 1.5-V battery, just like a torch. This convenient and economical setup may find applications in fields like tracer-gas detection or nondestructive evaluation.

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