# Spin-Related Micro-Photoluminescence in Fe\({}^{3+}\) Doped ZnSe Nanoribbons
## 3 Results and Discussion
The peak GFC1 originates from the bound exciton (BX) instead of the free exciton (FX) because it has lower energy than free excitons, and it can be confirmed later. The peak GFC3 should be attributed to the electron hole plasma (EHP) recombination emission, which has large full widths at half maximum (FWHM) and lower energy emission. At high power, higher carrier density is generated, which enhances carrier exchange interaction and leads to the band-gap renormalization of the nanoribbon [28], that is, it forms EHP recombination emission at high excited power and results in a red-shift of the emission peak [29]. This phenomenon is related to the photoheating by a CW laser. The GFC2 should be assigned to the emission of exciton magnetic polaron (EMP) due to the existence of ferromagnetic coupled Fe(III) cluster. At low excited power, the EMP emission in alio-valence ion doping ZnSe is not present, as shown in Figure 3b. The main elementary excitation of the near band-edge emission is bound excitons, and the EMP emission might be minor and merge with BX, so that EMP cannot be distinguished  
Figure 2: (a) X-ray diffractometer (XRD) pattern of as-prepared Fe doped ZnSe nanoribbons. The corresponding Miller indexes are labeled at the top of the diffraction peaks. The red line 1 is the experimental results of the Fe doped ZnSe nanoribbon, and the black line 2 is the Joint Committee on Powder Diffraction Standards (JCPDS) card of No. 37-1463 of pure ZnSe material; and (b) the micro-Raman spectrum of an individual Fe doped ZnSe nanoribbon with a continuous wave (CW) 532 nm laser as the excited source at room temperature. clearly. EMP can be enhanced at high excitation power due to larger binding energy, so a shoulder shows up at the long wavelength side of the near band-edge emission band (BX) at increasing powers. With further increasing power, a part of BX may dissociate into electron and hole to lead e-h plasma emission at around 493 nm due to excess charge effect of Fe\({}^{3+}\), while EMP emission become significant in nanoribbons, as marked by the red arrow in Figure 3b. In addition, the energy span of GFC1 and GFC2 is 64 meV, which is larger than the energy of LO phonons, which eliminates the possibility of LO phonon replicas [3]. Previous works studied the formation and emission of EMP in transition metal ion doped II-VI semiconductor belts, which demonstrates EMP emission at the long wavelength side of FX. For example, [PERSON] et al. researched the EMP behavior in Co doped CdS nanowires [30] and [PERSON] et al. reported Mn doped ZnSe nanowires [31]. Thus, the GFC2 could be assigned to the EMP emission. With increasing powers, the FWHM of near band-edge emission band BX increases super-linearly, as shown with the red curve of Figure 3d, which is often related to the giant spin splitting of exciton states in TM doped semiconductors [32]. Moreover, their intensity increases linearly, as shown with the black line in Figure 3d, which confirms that it is TM ion dopant related BX and not only EMP that dominate the luminescence. The previous exciton state is related to the spin of a single TM ion dopant to couple with FX in the TM doped semiconductor, while EMP was the FX coupling with a multi-spin ferromagnetic coupled cluster in DMS. In both systems, the phonon scatterings are very involved in their relaxations. Then, some EHP recombination emissions become significant at high excitation power [33]. Due to the narrow measuring range, the intensity of the BX emission has not yet reached saturation, which also indicates a dominant component of BX in the near band-edge emission but not carriers. Figure 3: **(a)** The photoluminescence (PL) spectrum of an individual Fe doped ZnSe nanoribbon with a 405 nm laser at excitation power \(P=3\) mW. The inset in the top right corner is the PL image of the nanoribbon in the dark field observation; **(b)** the power-dependent PL spectra of an individual Fe doped ZnSe nanoribbon at room temperature.