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An optoelectronic framework enabled by low-dimensional phase-change films

Abstract

The development of materials whose refractive index can be optically transformed as desired, such as chalcogenide-based phase-change materials, has revolutionized the media and data storage industries by providing inexpensive, high-speed, portable and reliable platforms able to store vast quantities of data. Phase-change materials switch between two solid states—amorphous and crystalline—in response to a stimulus, such as heat, with an associated change in the physical properties of the material, including optical absorption, electrical conductance and Young’s modulus1,2,3,4,5. The initial applications of these materials (particularly the germanium antimony tellurium alloy Ge2Sb2Te5) exploited the reversible change in their optical properties in rewritable optical data storage technologies6,7. More recently, the change in their electrical conductivity has also been extensively studied in the development of non-volatile phase-change memories4,5. Here we show that by combining the optical and electronic property modulation of such materials, display and data visualization applications that go beyond data storage can be created. Using extremely thin phase-change materials and transparent conductors, we demonstrate electrically induced stable colour changes in both reflective and semi-transparent modes. Further, we show how a pixelated approach can be used in displays on both rigid and flexible films. This optoelectronic framework using low-dimensional phase-change materials has many likely applications, such as ultrafast, entirely solid-state displays with nanometre-scale pixels, semi-transparent ‘smart’ glasses, ‘smart’ contact lenses and artificial retina devices.

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Figure 1: Colour tunability using ultrathin PCM films.
Figure 2: Reflective display films.
Figure 3: Semi-transparent display type films.
Figure 4: Flexible display films in both reflective and semi-transparent mode.
Figure 5: Demonstration of a single pixel.

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Acknowledgements

We thank R. Taylor for scientific discussions related to optical spectroscopy measurements. We are grateful to M. Riede for discussions on the modelling aspects of our study. This research was supported by EPSRC via grant numbers EP/J018783/1, EP/J018694/1 and EP/J00541X/2 as well as the OUP John Fell Fund.

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All authors contributed substantially to this work. P.H. and H.B. conceived and designed the experiments. P.H. performed the experiments with input from H. B and C.D.W. All authors analysed the data. The manuscript was written by P.H. and H.B. with input from C.D.W.

Corresponding author

Correspondence to Harish Bhaskaran.

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The authors declare no competing financial interests.

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Hosseini, P., Wright, C. & Bhaskaran, H. An optoelectronic framework enabled by low-dimensional phase-change films. Nature 511, 206–211 (2014). https://doi.org/10.1038/nature13487

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