A high-precision, template-assisted, anisotropic wet etching method for fabricating perovskite microstructure arrays

Cesium lead-halide (CsPbX3; X = Cl, Br, I) perovskite microstructure arrays have become the basis for laser array applications, due to their outstanding spectral coherence, low threshold, and wideband tunability. Furthermore, the common fabrication methods for these arrays have the limitation to achieve both tailored design and high resolution simultaneously. Herein, we report a high-precision, template-assisted, wet etching (TAWE) method for the preparation of perovskite microstructure arrays. This method possesses the advantages of flexible design, controllable size, and ultrahigh accuracy (the resolution can reach 1 μm or higher). A 20 × 20 inverted pyramid array with a diameter of 3 μm and a period of 4 μm was fabricated using this method. CsPbBr3 perovskite quantum dots fabricated by means of hot injection were filled into the inverted pyramid array via spin-coating and pumped using a laser with a wavelength of 400 nm. The lasing characteristics of the array were then measured and analyzed; the threshold was measured to be 37.6 μJ cm−2, and the full width at half maximum of the amplified spontaneous emission spectrum was found to be about 4.7 nm. These results demonstrate that perovskite microstructure arrays prepared via this method have potential applications in laser arrays.


Preparation of the CsPbBr 3 quantum dots.
(1) the Cs 2 CO 3 (0.8 g) were dissolved into the bottle mixed with the Octadecene (30ml) and the oleic acid(2.5ml), the Cesium oleate precursor was obtained until the reaction completely finished at a temperature of 150℃under the N 2 atmosphere (2) Mix the Octadecene (10ml), oleic acid(1ml), oleylamine (1mL) and lead bromide (0.36 mmol) in the bottle and heat to 180℃until the lead bromide dissolve completely at the N 2 atmosphere, and add the prefabricated Cesium oleate precursor (0.8ml) into the mixed solution.
(3) added some toluene and ethyl acetate into the mixed solution, take out the crystal precipitation at the bottom and redispersing in toluene, the CsPbBr 3 quantum dots is fabricated.

ASE and lasing Measurements.
For the ASE measurements, all experiments were conducted at room temperature. The excitation source used for this work was a Ti: sapphire oscillator/amplifier. The latter produced ~120 fs duration, 800 nm wavelength laser output with a repetition rate of 1 kHz. The output divergence angle after collimation was around 0.65 mrad. By using a beta barium borate (BBO) crystal, the output wavelength was converted to 400nm. The pump beam was focused by a lens on the sample, and the emission from the edge of the structure was collected by a spectrograph (spectrapro-300i, Acton research corporation).
1.4 Device Measurements. The electron beam lithography technology is using the equipment (Inspect F50, FEI).Transmission electron microscopy (TEM) images were taken with an accelerating voltage of 200 kV (Tecnai G20, FEI).The atomic Electronic Supplementary Material (ESI) for RSC Advances. This journal is © The Royal Society of Chemistry 2020 force microscope (AFM) were recorded using a microscope (Bioscope Resolve, Bruker).Scanning electron microscopy (SEM) images were taken with an accelerating voltage of 20 kV (Inspect F50, FEI). The absorption and PL intensity spectra were measured through a spectrophotometer (UV-3600, SHIMADZU) and spectrofluorophotometer (RF-5301PC, SHIMADZU) respectively.

Fig. S1 The diagram of TAWE method
The template assisted wet etching (TAWE) method main contains following steps: (1) A silica with a thickness of 30 nm was deposited on the silicon substrate through chemical vapor deposition.
(2) A PolyMethylMethacrylate (PMMA) photoresist with a thickness of 200 nm was spun on the sillica through spin coating.
(3) The graph designed in computer was transferred to the PMMA through the electron beam lithography technology.
(4) Mask structure was fabricated after development process.
(5) The sample was put into the HF solution to transfer the mask structure from PMMA to the sillica.
(6) Anisotropic wet etching of silicon was processed using an alkaline solution, and then, the PMMA was removed by the acetone.
(7) The sillica was removed by the HF solution.
(8) The Ag film with a thickness of 250 nm was coated through the thermal evaporation technology. A chromium film with a thickness of 10 nm is coated act as a adhesion layer. In order to ensure the quality of the silver film, it was necessary to keep at an appropriate temperature (150℃) during evaporation.
(9) The CsPbBr 3 quantum dots fabricated through hot injection is filled into the inverted pyramid micro-structure array through spin coating method, and a smooth CsPbBr 3 perovskite film can be formed in the micro-structure by cycling spin-coating and dry several times.