Ultra-long high quality catalyst-free WO ₃ nanowires for fabricating high-performance visible photodetectors

Abstract

Abstract This work presents a study on the controlled growth of WO 3 nanowires via chemical vapor deposition without catalyst, and their potential applications in visible photodetectors. The influence of growth conditions on the morphology of WO 3 nanowires is studied in order to understand the growth mechanism of WO 3 nanowires, and ultra-long (60 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>μ</mml:mi> <mml:mrow> <mml:mtext>m</mml:mtext> </mml:mrow> </mml:math> , the longest one ever reported) WO 3 nanowires with a spindle shape are achieved by optimizing the growth conditions. It was found that the length of WO 3 nanowires increases from 15 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>μ</mml:mi> <mml:mrow> <mml:mtext>m</mml:mtext> </mml:mrow> </mml:math> to 60 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>μ</mml:mi> <mml:mrow> <mml:mtext>m</mml:mtext> </mml:mrow> </mml:math> with increasing the argon carrier gas flow rate from 30 sccm to 90 sccm, and then saturates with further increasing the argon carrier gas flow rate. However, the length of WO 3 nanowires reduces from 60 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>μ</mml:mi> <mml:mrow> <mml:mtext>m</mml:mtext> </mml:mrow> </mml:math> to 19 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>μ</mml:mi> <mml:mrow> <mml:mtext>m</mml:mtext> </mml:mrow> </mml:math> with increasing the tube inner pressure from 2.5 Torr to 3.5 Torr. The photoconductor detectors based on WO 3 single nanowires present excellent device performance with a responsivity as high as 19 A W −1 at a bias of 0.1 V, a detectivity as high as 1.06 × 10 11 Jones, and a response (rising and decay) time as short as 8 ms under the illumination of a 404 nm laser. These results indicate the great potential of WO 3 nanowires for applications in fabricating high performance visible photodetectors.