Production and characterization of Nd,Cr:GSGG thin films on Si(001) grown by pulsed laser ablation

Abstract

Nd,Cr:Gd 3 Sc 2 Ga 3 O 12 (GSGG) thin films have been produced for the first time. They were grown on Si(001) substrates at 650 • C by pulsed laser ablation at 248 nm of a crystalline Nd,Cr:GSGG target rod. The laser plume was analyzed using time-of-flight quadrupole mass spectroscopy, and consisted of elemental and metal oxide fragments with kinetic energies typically in the range 10 to 40 eV, though extending up to 100 eV. Although films deposited in vacuum using laser fluences of 0.8 ± 0.1 J cm −2 reproduced the Nd,Cr:GSGG bulk stoichiometry, those deposited using fluences above ≈ 3 J cm −2 resulted in noncongruent material transfer and were deficient in Ga and Cr. Attempts to grow films using synchronized oxygen or oxygen/argon pulses yielded mixed oxide phases. Under optimal growth conditions, the films were heteroepitaxial, with GSGG(001)[100] Si(001)[100], and exhibited VolmerWeber-type growth. Room-temperature emission spectra of the films suggest efficient non-radiative energy transfer between Cr 3+ and Nd 3+ ions, similar to that of the bulk crystal. PACS: 42.70.Hj; 78.66.Nk; 81.15.FgGadolinium scandium gallium garnet, Gd 3 Sc 2 Ga 3 O 12 (GSGG) doped with Nd and Cr has been shown to be an excellent solid-state lasing medium for high-efficiency Ndlasers [1, 2]. Nd 3+ ions in crystals have very narrow absorption linewidths and hence flashlamp pumping efficiency is poor. Nd 3+ can, however, be sensitized by also introducing Cr 3+ ions which absorb over a broad visible range and can rapidly transfer their energy by non-radiative processes to the Nd 3+ ions. GSGG offers the most efficient energy transfer from Cr 3+ to Nd 3+ ions of the various doublydoped garnet crystals investigated to date, due to its coactive crystal fields [3]. When flashlamp-pumped, the 1.06 µm 4 F 3/2 → 4 I 11/2 laser transition of Nd 3+ has been shown to be several times more efficient in Nd,Cr:GSGG than in the leading commercial host, Nd-doped yttrium aluminum garnet [3][4][5].There is an increasing interest in growing thin films of solid-state laser materials on semiconductor substrates, with a view to integrated semiconductor-optoelectronic applications such as active planar waveguides and optical masers [6,7], though this is the first report on the deposition of GSGG films. The thermal focusing effects observed in the bulk crystals, which limits the application of Nd,Cr:GSGG as a highpower lasing medium [8], is negligible in thin films because of their small thickness. The successful deposition of Nd,Cr:GSGG films on Si substrates by PLD could therefore lead to the development of microlasers with in situ semiconductor diode laser pumping [9]. Diode pumping has the advantage over flashlamp pumping that the Nd 3+ absorption line can be directly and efficiently pumped, thereby dispensing with the need to incorporate Cr 3+ ions.Pulsed laser deposition (PLD) is a technique uniquely suited to the deposition of multielemental thin films [10,11], because of its capacity to transfer material congruently from bulk to film in a single step....

Growth and magnetism of metallic thin films and multilayers by pulsed-laser deposition

“…Here, PLD holds its classical advantage of stoichiometric transfer of materials with complex composition. Even very complicated compounds such as Nd-and Cr-doped gadolinium-scandium-gallium garnet, which contains six elements and 160 atoms in a unit cell, can be grown epitaxially on Si(0 0 1) substrate [120]. In the following, we describe some recent applications of PLD in growing thin films of both soft and hard multicomponent magnetic alloys.…”

Effect of laser parameters on the measurement of U/Nd ratio using pulsed laser deposition followed by isotopic dilution mass spectrometry

“…Hence, one would expect the relative partial pressure of oxygen in the plume be less, thereby the NdO fraction will also be less. Moreover, at these high power densities, the velocity of the vapor species in the plume will be high [36] and the corresponding sticking coefficients on the substrate can also vary [37], leading to small variations in the atom ratio of U/Nd in the film.…”

Laser ablation of La0.9Sr0.1Ga0·8Mg0.2O2.85 — plume and film characterization

“…These analyses show that the ion kinetic energies in the present case are of the order of 5 eV and hence the ion resputtering effect causing deficiency in the vacuum deposited films is unlikely. However, such effects are known to dominate when the ion energies are of the order of 50 eV [19].…”