High-quality, uniform, one-dimensional (1D) lanthanum hexaboride (LaB 6 ) nanostructures with different morphologies (for example, sparse or dense nanoneedles, or nanorods and nanowire arrays) were fabricated through an effective, easily controlled, one-step, catalyst-free chemical vapor deposition process. The morphologies, structures and temperature-dependent field emission (FE) properties were systematically investigated. FE measurements at room temperature (RT) showed that LaB 6 nanowire arrays possess the best FE characteristics among all 1D LaB 6 nanostructures, with a low turn-on electric field (E to , 1.82 V lm À1 ), a low threshold electric field (E thr , 2.48 V lm À1 ), a high current (5.66 mA cm À2 at 2.92 V lm À1 ) and good stability (at a testing time of 1000 min, fluctuations were o6.0%). Temperature-dependent FE showed that the turn-on and threshold electric fields decreased from 1.82 to 1.06 and 2.48 to 1.62 V lm À1 , respectively, whereas the emission current density increased significantly from 0.20 to 9.05 mA cm À2 at 2.20 V lm À1 when the temperature was increased from RT to 723 K. The emission current density and the dependence of the effective work function on temperature were also investigated. We attribute the significant reduction of the turn-on and threshold fields and the remarkable increase of emission current to a decrease in the effective work function with temperature.

High‐quality NdB6 nanostructures with a low work function are successfully synthesized via an one‐step catalyst‐free chemical vapor deposition process. Field emission properties of these nanostructures (curve nanowires, short‐straight nanorods, long‐straight nanowires, and nanoneedles) are systematically investigated and found to be strongly affected by the tip morphologies and temperatures. The nanoneedles with sharp tips demonstrate the lowest turn‐on (2.71 V/μm) and threshold (3.60 V/μm) electric fields, as well as a high current density (5.37 mA/cm2) at a field of 4.32 V/μm in comparision with other nanostructures. Furthermore, with an increase in temperature from room temperature to 623 K, the turn‐on field of the nanoneedles decreases from 2.71 to 1.76 V/μm, and the threshold field decreases from 3.60 to 2.57 V/μm. Such excellent performances make NdB6 nanomaterials promising candidates for application in flat panel displays and nanoelectronics building blocks.

On page 5038 J. Q. Xu, T. Y. Zhai and co-workers develop an effective chemical vapor deposition process to fabricate high-quality NdB6 nanoneedles with an ultra-low work function. These nanoneedles exhibit excellent field-emission performance with a low turn-on/threshold field, a high current density, and good stability. Such a simple synthesized procedure can be readily extended to the synthesis of RB 6 (R = rare earth) and related boride nanostructures.

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