Semiconductor quantum dot structure and method for making the same

A method for making semiconductor quantum dot structures, comprising the steps of:

• (a) mixing a solution containing a precursor of M1 with a solution containing a precursor of C1 to form a first mixture solution;
• (b) heating the first mixture solution to a first temperature not lower than a nucleation temperature of a first compound M1C1 for a first predetermined time period so as to form a plurality of seed crystals (21) of the first compound M1C1 in the first mixture solution, each of the seed crystals (21) having a crystal surface that has a plurality of first regions (211) and a plurality of second regions (212), each of the first regions (211) being inactive with oxygen, each of the second regions (212) being oxidized by oxygen present in the first mixture solution so as to form an oxide layer thereon;
• (c) forming a second mixture solution by continuously adding an additional solution containing the precursor of M1, an addition solution containing the precursor of C1, and a first diluted fluoride-containing etchant into the first mixture solution obtained after step (b) for a second predetermined time period, while keeping at the first temperature, so as to permit the oxide layer formed on each of the second regions (212) of the seed crystals (21) to be etched by the first diluted fluoride-containing etchant, and so as to grow a plurality of core layers (22) of the first compound M1C1 respectively on the seed crystals (21), each of the core layers (22) having a plurality of first areas (221) and a plurality of second areas (222), the first areas (221) of each of the core layers (22) being respectively grown on the first regions (211) of a corresponding one of the seed crystals (21), the second areas (222) of each of the core layers (22) being respectively grown on the second regions (212) of a corresponding one of the seed crystals (21), each of the first areas (221) having a thickness greater than that of each of the second areas (222), the first diluted fluoride-containing etchant having a concentration ranging from 1 vol % to 5 vol % and a volume ranging from 0.1 mL to 2.0 mL;
• (d) forming a third mixture solution by continuously adding a solution containing a precursor of X1 or a solution containing a precursor of X2 into the second mixture solution obtained after step (c) for a third predetermined time period so as to allow growth of a plurality of barrier layers (23) respectively on the core layers (22), thereby obtaining, in the third mixture solution, a plurality of cores (2) each including one of the seed crystals (21), a corresponding one of the core layers (22) and a corresponding one of the barrier layers (23), each of the barrier layers (23) being made of a second compound selected from the group consisting of M1X1 and X2C1;
• (e) removing the cores (2) from the third mixture solution and dispersing the cores (2) in a clear solution including a precursor of M2 so as to obtain a clear solution including the cores (2) and the precursor of M2;
• and
• (f) heating the clear solution including the cores (2) and the precursor of M2 to a second temperature not lower than a nucleation temperature of a third compound M2C2, and then adding a solution containing a precursor of C2, so as to grow a plurality of shells (3) respectively on the barrier layers (23) of the cores (2), thereby obtaining the semiconductor quantum dot structures each including one of the cores (2) and a corresponding one of the shells (3),
• wherein
• M1 is a group Ill element selected from the group consisting of Al, Ga, In, and combinations thereof;
• and C1 is a group V element selected from the group consisting of P, As, and a combination thereof,
• X1 is an element selected from the group consisting of N, As, S, Se, Te, F, Cl, Br, and I;
• and X2 is an element selected from the group consisting of Na, K, Cs, Mg, Cu, Zn, Cd, Hg, Al, Ga, and Pb, and
• M2 is a group II element selected from the group consisting of Zn, Cd, and a combination thereof;
• and C2 is a group VI element selected from the group consisting of S, Se, O, Te, and combinations thereof.