Structure and Luminescence of 2D Dilute Magnetic Semiconductors:  Cd_1-xMn_xSe·L_0.5 (L = Diamines)

Abstract

The two-dimensional (2D) dilute magnetic semiconductors Cd 1-x Mn x Se‚L 0.5 (L ) ethylenediamine, or en, and 1,6-hexanediamine, or hda, x ) 0-0.8) were synthesized in an autoclave at 120 °C. Ab initio structure solution from X-ray powder diffraction reveals the host compound CdSe‚hda 0.5 (space group, Pbca, a ) 6.8852 Å, b ) 6.7894 Å, c ) 27.4113 Å) is structurally analogous to CdSe‚en 0.5 , except for a subtle difference in alignment of aliphatic diamine ligandssthe hda molecule deflects from the c axis and inclines toward the b axis. CdSe‚L 0.5 shows well-defined UV absorption and emission peaks, which is attributed to a 2D exciton band edge transition due to size confinement effect in the c direction and the only photoemission level is the 2D exciton ground state with a long lifetime (7 µs) and intrinsic line width (177 meV) at room temperature. When Cd 2+ is partly substituted by Mn 2+ , a strong Mn 2+ -related luminescence peak at 2.12 eV (584 nm) is obtained at room temperature, which can be assigned to Mn 2+ internal transition ( 4 T 1 f 6 A 1 ); its excitation peak overlaps with the photoemission peak of the 2D exciton ground state which indicates that the Mn 2+ emission is driven by the 2D exciton ground-state transition. For x ) 0.02, the photoluminescence intensity of Cd 1-x Mn x Se‚hda 0.5 reaches maximum and enhances 28 times compared with that of Cd 1-x Mn x Se‚en. When x < 0.05, the Mn 2+ luminescence is a characteristic single-exponential decay process with a well-defined constant lifetime of 375 µs. Electron spin resonance spectra show that Mn 2+ substitutes Cd 2+ ion and forms a [MnSe 3 N] coordination tetrahedron and that there are isolated Mn 2+ luminescence centers in Cd 1-x Mn x Se‚hda 0.5 (x < 0.05), which is the key factor for their stronger luminescence character compared to Cd 1-x Mn x Se‚en 0.5 .

A New Class of Nanostructured Inorganic–Organic Hybrid Semiconductors Based on II–VI Binary Compounds

“…32. As a well-known strong luminescent center, Mn 2 þ is used here to enhance the photoluminescence intensity (173,206,207). The chromaticity coordinates of these white light LEDs fall well within the white region of the International Commission on Illumination (CIE) 1931 color space chromaticity diagram (208).…”

“…Magnetic elements (e.g., manganese, iron, and cobalt) could be incorporated into nonmagnetic hybrid compounds, such as 3D-[ZnSe(L) 1/2 ], 3D-[CdSe(L) 1/2 ], 2D-[ZnSe(ba)], and 2D-[Zn 2 Se 2 (ba)] keeping the crystal structures intact (110,173,(226)(227)(228)(229)(230). The absorption spectra of magnetically substituted hybrids also display a large blue shift, the extent of which depends on the amount of magnetic substituents.…”

Synthesis of Semiconducting Functional Materials in Solution: From II‐VI Semiconductor to Inorganic–Organic Hybrid Semiconductor Nanomaterials

“…[121][122][123][124] While possessing uniform and periodic crystal structures, the resultant threedimensional networks [MQ(L) 0.5 ] (M ¼ Mn, Zn, Cd; Q ¼ S, Se, Te; L ¼ diamine, deta) hybrid structures, exhibit a very large blue shift in their optical adsorption edge due to a strong quantum confinement effect (QCE) induced by the internal sub-nanostructures. [17,18,121] These compounds exhibit significantly enhanced electronic and optical properties, [121,[125][126][127][128][129][130] including tunable band gap as a result of strong quantum confinement effect (blue shifts up to $2 eV) and high bandedge absorption (e.g., 10-20 times higher in 3D-ZnTe(en) 0.5 compared to bulk GaAs) (Fig. 9).…”

Synthesis of Inorganic–Organic 2D CdSe Slab‐Diamine Quantum Nets

“…[7] Another example is the family of II-VI-based inorganic-organic lamellar-type hybrid materials, A II B VI (en) 0.5 (A = Cd, Zn; B = S, Se, Te; en = ethylenediamine) synthesized by solvent coordination molecular template methods. [12][13][14][15][16][17][18][19][20][21] In these materials, the ultrathin semiconductor inorganic 2D slabs are intercalated with organic diamines, providing not only an ideal model system for fundamental study but also free-standing quantum wells for optoelectronic applications.Porous semiconductors have been recognized as a unique class of nanomaterials due to their low density, high surface area, and large open pores. [22][23][24][25][26][27][28][29][30][31][32][33] Typically, these materials are formed via the sol-gel assembly of semiconductor nanoparticles into aerogel networks by chemical bridging of nanoparticles.…”

“…[7] Another example is the family of II-VI-based inorganic-organic lamellar-type hybrid materials, A II B VI (en) 0.5 (A = Cd, Zn; B = S, Se, Te; en = ethylenediamine) synthesized by solvent coordination molecular template methods. [12][13][14][15][16][17][18][19][20][21] In these materials, the ultrathin semiconductor inorganic 2D slabs are intercalated with organic diamines, providing not only an ideal model system for fundamental study but also free-standing quantum wells for optoelectronic applications.…”