Synthesis and defect control of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>Sr</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:msub> <mml:mi>IrO</mml:mi> <mml:mn>4</mml:mn> </mml:msub> </mml:mrow> </mml:math>

<a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:msub> <a:mi>Sr</a:mi> <a:mn>2</a:mn> </a:msub> <a:msub> <a:mi>IrO</a:mi> <a:mn>4</a:mn> </a:msub> </a:mrow> </a:math> (Sr214) and related iridates have emerged as key platforms for fundamental correlated-electron physics and for potential applications such as magnonics. Here, we report the epitaxial growth of high-quality Sr214 thin films using reactive off-axis sputtering. Conventional pulsed-laser deposition of Sr214 suffers from limitations arising from the volatility and decomposition of iridates, which often result in parasitic Ruddlesden–Popper phases and iridium vacancies. By employing sputtering, we mitigate these issues and achieve stable growth conditions that allow precise mapping of the phase diagram. Systematic variation of the growth temperature reveals that Sr214 stabilizes within a window between <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"> <b:mrow> <b:mn>825</b:mn> <b:msup> <b:mspace width="4pt"/> <b:mo>∘</b:mo> </b:msup> <b:mi mathvariant="normal">C</b:mi> </b:mrow> </b:math> and <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"> <e:mrow> <e:mn>1050</e:mn> <e:msup> <e:mspace width="4pt"/> <e:mo>∘</e:mo> </e:msup> <e:mi mathvariant="normal">C</e:mi> </e:mrow> </e:math> , with optimal crystallinity and thickness obtained at <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"> <h:mrow> <h:mn>840</h:mn> <h:msup> <h:mspace width="4pt"/> <h:mo>∘</h:mo> </h:msup> <h:mi mathvariant="normal">C</h:mi> </h:mrow> </h:math> . Raman spectroscopy provides sensitive diagnostics of iridium vacancies, with defect-induced phonon modes and peak intensity ratios correlating strongly with the <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"> <k:mi>c</k:mi> </k:math> -axis lattice parameter. Our results establish reactive sputtering as a robust route for integrating Sr214 into oxide electronic and magnonic device architectures.