To date, researchers have confirmed the presence of more than 500 color centers. [8] Among them, the silicon-vacancy (SiV) color center exhibits an optical emission with a zero-photo line (ZPL) centered at 738 nm along with a narrow peak width at room temperature, which concentrates more than 70% of its signals. [9,10] This means that SiV centers have excellent performance in the areas of bio-labeling and nanothermometry. Generally, these applications demand high concentration or photoluminescence (PL) intensity. An efficient way of meeting this requirement is to dope sufficient Si atoms or SiV centers in diamonds, utilizing a silicon-containing gas precursor. [11,12] However, due to the large refractive index (about 2.4) of diamonds as well as the formation of sp 2 amorphous carbon or graphite phase, efficient PL extraction of color centers in polycrystalline diamond films remains a challenge. [13][14][15][16] Numerous approaches have been proposed to improve the PL emission of color centers. Of these, the etching of sp 2 carbon species to optimize crystalline quality has been confirmed to remarkably increase PL attributes in nanocrystalline diamonds. [15] Another approach to optimizing the PL emission of color centers in nanocrystalline diamond is to alter the surface termination from hydrogen to oxygen. [17][18][19][20][21] In comparison, these two methods have a negligible effect on increasing the PL of monocrystalline/polycrystalline diamonds. Other approaches, such as coupling color centers with photonic crystals [22][23][24] or micro/nano structures, [14,25] have been demonstrated to be viable for increasing the optical collection efficiency of microsized diamonds. For example, Ondic et al. [23] prepared 2D polycrystalline diamond photonic crystal slabs using a bottom-up approach, tuning the leaky modes to increase the PL intensity of SiV centers by 14 fold. However, the design of an accurate mask is highly critical in this approach to the subsequent etching and deposition processes, which is complicated and of high cost. Additionally, Insitu formed hetero-particles, [26] as well as diamond nanoparticles, [27,28] were also utilized as masks to fabricate 1D nanostructures during the reactive ion etching of diamond films. The realization of such a structure was dependent on the conductivity of the film. [27] Recently, it was reported that by annealing diamond particles in the air, a nanopyramid or irregular nanoporous structure was formed on their surface, resulting in aThe optically active silicon-vacancy (SiV) center in diamonds is an excellent candidate for quantum photonics and sensing applications. To date, optimizing the photoluminescence (PL) collection efficiency of SiV centers has proven difficult. To address this issue, the current study presents a simple two-step method for preparing single-crystalline diamond nanoneedle arrays. In the first step, silicon-doped (001) textured diamond films are deposited with a mixture of microcrystalline and nanocrystalline grains in a microwave plasma CVD (MPCVD)...